moved Api17+ stuff into separate DeviceApi17 class to prevent verify failures on older api's
fixed startup error
added DeviceApi17 class to separate out Api17+ stuff
Added open_cellid_api_key support to gradle.properties
made gradle.properties optional
Merge pull request #146 from tobykurien/master

Fix for crash of Cell Info on Android 4.2
Verified all links to solve #150
Update CONTRIBUTING.md