Use Android Maven plugin 3.8.0.

This should be compatible with Maven 3.1.
Update to Android Maven Plugin 3.8.2.
Merge branch 'maven31'
Update gradle and Android plugin versions.
Don't fail on lint errors.
Use gradle with sources.
Refactor IntentIntegrator to be more flexible.
1.1.5 bump.
1.2.0. Drop support for apklibs.
Merge branch 'develop'
Bump version in readme example.
Add "Sponsored by Journey".
Fix Android SDK installation on Travis.
Switch to new Travis Android support.
Modify and merge #10.
Add instructions for usage from a Fragment.

Fixes #8.
Move library into a subfolder.
Add a sample project.

This greatly speeds up the development/test cycle.
Merge branch 'sample-project'
Add release script.