convert storm-cassandra, storm-jms, and storm-signals to git submodules
add information for storm-contrib submodules.
converted storm-contrib subprojects to git submodules (most hosted under github.com/stormprocessor
Merge branch 'master' of github.com:nathanmarz/storm-contrib into submodules-merge

Conflicts:
	storm-backport
	storm-benchmark
	storm-cassandra
	storm-growl
	storm-growl/README.markdown
	storm-growl/pom.xml
	storm-growl/src/main/java/storm/growl/GrowlBolt.java
	storm-growl/src/main/java/storm/growl/TestGrowlTopology.java
	storm-hbase
	storm-jms
	storm-redis-pubsub
	storm-scribe
	storm-signals
	storm-state
Merge pull request #25 from ptgoetz/submodules

Start using git submodules in storm-contrib