add waffle.io badge
Merge pull request #83 from waffle-iron/master

waffle.io Badge
Update README.md
Update README.md

Fix travis badge.
Merge branch 'master' into dev

Conflicts:
	README.md
Move from slf4j-android to android-logger.

AndroidLogger is more flexible than slf4j-android, and allows us to set
per-package logging cutoffs. Also, it is smaller in size.