Added support to publish binaries to bintray (requires gradle 2.0)

#46 This pull request contains bintray support changes. The changeset contains 2 parts:
* Switch to gradle 2.0 (required by the bintray publishing plugin)
* Changes to **build.gradle** and **gradle.properties**.

Please review **gradle.properties** and create an account and repository on https://bintray.com according to your preferences. _NOTE: You have to replace `project_bintray_repo` and `project_bintray_org` properties in **gradle.properties** file._

P.S. Implemented during Basel Hackergarten (@hackergarten).