Add check style configuration
Apply new check style to draggablepanel module
Apply new check style to sample module
Fix more check style problems.
Add checkstyle task to CI
Fix .travis.yml configuration
Update max line length from 100 to 120
Merge branch 'develop' into fix-horizontal-drag-problems

Conflicts:
	draggablepanel/src/main/java/com/github/pedrovgs/DraggableView.java
	draggablepanel/src/main/java/com/github/pedrovgs/DraggableViewCallback.java
	draggablepanel/src/main/java/com/github/pedrovgs/transformer/ResizeTransformer.java
	draggablepanel/src/main/java/com/github/pedrovgs/transformer/ScaleTransformer.java