Add a TODO explaining use of app target in pingpong, update README.
Merge pull request #162 from wfarner/wfarner/pingpong_todo

Add a TODO explaining use of app target in pingpong, update README.
Bugfix in AnnotationProcessor handling of exclusives.
Simplify NailgunTask.

Gets rid of the pidfile. Locates nailguns using find() in
all cases.
Merge remote-tracking branch 'twitter/master'
AnnotationProcessor bug was already fixed...
Make ng spawning thread-safe.