Merge pull request #6 from KeithYokoma/master

Support for fragments on account authentication activity
Fix trivis.yml
Remove unused code
Fix README
Fix test/AndroidManifest.xml
Make up project with gradle style
Merge pull request #7 from KeithYokoma/gradle_build

Make up project with gradle style
Move examples to gradle styled module

あわせて、使用しなくなったディレクトリの整理も