Update build tools to 21.1.1
Update Gradle wrapper to 2.1
Update Android Gradle plug-in to 0.14.1
Fix deprecation warning
Fix PMD ruleSets
Update compile and target SDK to 21
Update dependencies
Fix Lint warnings
Remove useless parentheses
Update OkHttp to 2.0.0
Merge pull request #2 from friederbluemle/update-project

Various project updates