#39 Conversion of Android build to Gradle

Here is my work so far along this stream. Points to note
* The maven build has not been disabled and should still work fine pending on QA of the Gradle build and update of Travis and Snap
* Though calabash gradle plugin has been added its integration needs to be properly tested and polished so recommend we continue using external `calabash run <apk>` at the command line.
* Some minor compatibility issues with Hamcrest matchers demanded minor code changes to the tests that should be review
* Documentation has not been updated pending on review/acceptance of these changes