Fixed a typo
Added custom logger

The logger adds information on which
thread is the message logged
Merge pull request #17 from tehmou/feature/custom-logger

[REVIEW] Added custom logger
Changed build.gradle to make lambda expressions to work
Added some examplary lambda expressions for testing
Merge pull request #18 from tehmou/feature/introduce-working-retrolambda

[REVIEW] Introduce working retrolambda
Wrap TouchDeltaListener output into custom events
Expose TouchDeltaEvents to MapViewModel
- Add mechanism to load tiles when dragging stops
- Add mechanism to load tiles when zoom level changes
- More logging