I don't have the exact coding (at the moment since I'm not back in my room) I used in my project but I believe what I did was add all of the libraries necessary to Unirest.io as well as importing the jar file (after putting it into my lib folder) they have available here: http://oss.sonatype.org/content/repositories/releases/com/mashape/unirest/unirest-java/1.4.5/unirest-java-1.4.5.jar
In the dependencies portion I added something like this:
compile 'org.json:json:20140107'
compile 'org.apache.httpcomponents:httpclient:3.6'
compile 'org.apahe.httpcomponents:httpasyncclient:4.0.2'
compile 'org.apache.httpcomponents:httpmime:4.3.6'
into the dependencies {} portion of the build.gradle file along with the Unirest jar in the lib folder.
