Exclude IDE specific folder from version control.

+ Since files and folders are removed here
  you need to re-import the project into Android Studio.
Update Gradle plugin to v.0.13.0 and Gradle to v.2.1.

+ Update build tools to v.19.1.0.
Describe how to use the app.
Colorize layout elements for Android Studio preview.
Merge pull request #3 from johnjohndoe/update-project

Update project