FLUME-2909. Upgrade RAT to 0.11
FLUME-2909. Upgrade RAT to 0.11

This allows command-line override of RAT using the command mvn -Drat.skip=true
which is useful in a development environment.

(Bessenyei Balázs Donát via Mike Percy)

iaiengxia/flume,szaboferee/flume,szaboferee/flume,szaboferee/flume,tinawenqiao/flume,iaiengxia/flume,tmgstevens/flume,tmgstevens/flume,tinawenqiao/flume,tinawenqiao/flume,tinawenqiao/flume,iaiengxia/flume,tmgstevens/flume,szaboferee/flume,iaiengxia/flume,tmgstevens/flume