Pow not loading gem properly while rails s works

I have an error when using pow, but it works perfectly with rails s. Here is the results of the same code on Heroku: www.contakapp.com

I believe the chunky_png-1.2.8 is from the foundation gem or some related issue. So I am also providing my whole gem file:

source 'https://rubygems.org'
ruby '1.9.3'

gem 'rails', '4.0.0'

#views
gem 'jquery-rails'            , '~> 2.2.1'
gem 'haml-rails'              , '~> 0.4'

#auth
gem 'omniauth-facebook'       , '~> 1.4.0'
gem 'omniauth-linkedin'       , '~> 0.1.0'

#API
gem 'twitter'                 , '~> 4.8.1'
gem 'rest-client'             , '~> 1.6.7'


# models
gem 'pg'

gem 'coffee-rails'
gem 'uglifier'
gem "font-awesome-rails"
gem 'sass-rails'
gem "compass-rails",    github: "milgner/compass-rails", ref: "1749c06f15dc4b058427e7969810457213647fb8"
gem "zurb-foundation", "~> 4.3.0"

group :development, :test do

end

group :development do

end

group :production, :staging do
    gem 'rails_12factor'
end

gemfile.lock

GIT
  remote: git://github.com/milgner/compass-rails.git
  revision: 1749c06f15dc4b058427e7969810457213647fb8
  ref: 1749c06f15dc4b058427e7969810457213647fb8
  specs:
    compass-rails (1.0.3)
      compass (>= 0.12.2, < 0.14)

GEM
  remote: https://rubygems.org/
  specs:
    actionmailer (4.0.0)
      actionpack (= 4.0.0)
      mail (~> 2.5.3)
    actionpack (4.0.0)
      activesupport (= 4.0.0)
      builder (~> 3.1.0)
      erubis (~> 2.7.0)
      rack (~> 1.5.2)
      rack-test (~> 0.6.2)
    activemodel (4.0.0)
      activesupport (= 4.0.0)
      builder (~> 3.1.0)
    activerecord (4.0.0)
      activemodel (= 4.0.0)
      activerecord-deprecated_finders (~> 1.0.2)
      activesupport (= 4.0.0)
      arel (~> 4.0.0)
    activerecord-deprecated_finders (1.0.3)
    activesupport (4.0.0)
      i18n (~> 0.6, >= 0.6.4)
      minitest (~> 4.2)
      multi_json (~> 1.3)
      thread_safe (~> 0.1)
      tzinfo (~> 0.3.37)
    arel (4.0.0)
    atomic (1.1.10)
    bcrypt-ruby (3.0.1)
    builder (3.1.4)
    chunky_png (1.2.8)
    coffee-rails (4.0.0)
      coffee-script (>= 2.2.0)
      railties (>= 4.0.0.beta, < 5.0)
    coffee-script (2.2.0)
      coffee-script-source
      execjs
    coffee-script-source (1.6.3)
    compass (0.12.2)
      chunky_png (~> 1.2)
      fssm (>= 0.2.7)
      sass (~> 3.1)
    erubis (2.7.0)
    execjs (1.4.0)
      multi_json (~> 1.0)
    faraday (0.8.7)
      multipart-post (~> 1.1)
    font-awesome-rails (3.0.2.0)
      railties (>= 3.1)
    fssm (0.2.10)
    haml (4.0.1)
      tilt
    haml-rails (0.4)
      actionpack (>= 3.1, < 4.1)
      activesupport (>= 3.1, < 4.1)
      haml (>= 3.1, < 4.1)
      railties (>= 3.1, < 4.1)
    hashie (1.2.0)
    hike (1.2.3)
    httpauth (0.2.0)
    i18n (0.6.4)
    jquery-rails (2.2.1)
      railties (>= 3.0, < 5.0)
      thor (>= 0.14, < 2.0)
    jwt (0.1.8)
      multi_json (>= 1.5)
    mail (2.5.4)
      mime-types (~> 1.16)
      treetop (~> 1.4.8)
    mime-types (1.23)
    minitest (4.7.5)
    multi_json (1.7.7)
    multipart-post (1.2.0)
    oauth (0.4.7)
    oauth2 (0.8.1)
      faraday (~> 0.8)
      httpauth (~> 0.1)
      jwt (~> 0.1.4)
      multi_json (~> 1.0)
      rack (~> 1.2)
    omniauth (1.1.3)
      hashie (~> 1.2)
      rack
    omniauth-facebook (1.4.0)
      omniauth-oauth2 (~> 1.0.2)
    omniauth-google (1.0.2)
      multi_json
      omniauth (~> 1.0)
      omniauth-oauth
    omniauth-linkedin (0.1.0)
      omniauth-oauth (~> 1.0)
    omniauth-oauth (1.0.1)
      oauth
      omniauth (~> 1.0)
    omniauth-oauth2 (1.0.3)
      oauth2 (~> 0.8.0)
      omniauth (~> 1.0)
    omniauth-twitter (1.0.0)
      multi_json (~> 1.3)
      omniauth-oauth (~> 1.0)
    pg (0.15.1)
    polyglot (0.3.3)
    rack (1.5.2)
    rack-test (0.6.2)
      rack (>= 1.0)
    rails (4.0.0)
      actionmailer (= 4.0.0)
      actionpack (= 4.0.0)
      activerecord (= 4.0.0)
      activesupport (= 4.0.0)
      bundler (>= 1.3.0, < 2.0)
      railties (= 4.0.0)
      sprockets-rails (~> 2.0.0)
    rails_12factor (0.0.2)
      rails_serve_static_assets
      rails_stdout_logging
    rails_serve_static_assets (0.0.1)
    rails_stdout_logging (0.0.1)
    railties (4.0.0)
      actionpack (= 4.0.0)
      activesupport (= 4.0.0)
      rake (>= 0.8.7)
      thor (>= 0.18.1, < 2.0)
    rake (10.1.0)
    rest-client (1.6.7)
      mime-types (>= 1.16)
    sass (3.2.9)
    sass-rails (4.0.0)
      railties (>= 4.0.0.beta, < 5.0)
      sass (>= 3.1.10)
      sprockets-rails (~> 2.0.0)
    simple_oauth (0.2.0)
    sorcery (0.8.2)
      bcrypt-ruby (~> 3.0.0)
      oauth (~> 0.4.4)
      oauth2 (~> 0.8.0)
    sprockets (2.10.0)
      hike (~> 1.2)
      multi_json (~> 1.0)
      rack (~> 1.0)
      tilt (~> 1.1, != 1.3.0)
    sprockets-rails (2.0.0)
      actionpack (>= 3.0)
      activesupport (>= 3.0)
      sprockets (~> 2.8)
    thor (0.18.1)
    thread_safe (0.1.0)
      atomic
    tilt (1.4.1)
    treetop (1.4.14)
      polyglot
      polyglot (>= 0.3.1)
    twitter (4.8.1)
      faraday (~> 0.8, < 0.10)
      multi_json (~> 1.0)
      simple_oauth (~> 0.2)
    tzinfo (0.3.37)
    uglifier (2.1.2)
      execjs (>= 0.3.0)
      multi_json (~> 1.0, >= 1.0.2)
    zurb-foundation (4.3.0)
      sass (>= 3.2.0)

PLATFORMS
  ruby

DEPENDENCIES
  coffee-rails
  compass-rails!
  font-awesome-rails
  haml-rails (~> 0.4)
  jquery-rails (~> 2.2.1)
  omniauth-facebook
  omniauth-google
  omniauth-linkedin
  omniauth-twitter
  pg
  rails (= 4.0.0)
  rails_12factor
  rest-client (~> 1.6.7)
  sass-rails
  sorcery
  twitter (~> 4.8.1)
  uglifier
  zurb-foundation (~> 4.3.0)

It looks like Pow isn't using the same Ruby as your shell session. You can learn how to properly setup Pow with the same version of Ruby using your Ruby version manager in the Pow User Manual.