add data flow docs
Merge branch 'master' of github.com:metamx/druid
add link to data flow from druid cluster tutorial
fix typo in intro tutorial
Fixes for indexing service.

- Create IndexingServiceFirehoseModule so firehoses can be loaded by all mains
- Fix implicit lock acquisition in AbstractTask
Merge branch 'master' into indexing-service-realtime
IndexingServiceFirehoseModule: Add header
Merge pull request #271 from metamx/indexing-service-realtime

Indexing service fixes, targeted at RealtimeIndexTask
fix more docs
[maven-release-plugin] prepare release druid-0.6.0
[maven-release-plugin] prepare for next development iteration