Uncomment SSL option, throw RuntimeException from getFactory

This is a combination of 2 commits:

commit e68960667aee7265538bc04b363095bc29b669dd
Author: daurnimator <quae@daurnimator.com>
Date:   Tue Apr 30 15:11:00 2013

    getFactory shouldn't throw. Use a RuntimeException instead.

commit 63c62b5550cd2cf7ca533bd10e8c381496c51484
Author: daurnimator <quae@daurnimator.com>
Date:   Mon Apr 29 19:04:39 2013

    Uncomment SSL option
Move SSL config option to Constants
Merge branch 'master' into cdh-4.1.2
Tidy-up RabbitMQSource: whitespace, unthrown Exception

 -- rewrite tabs as spaces
 -- remove double blank lines
 -- remove declared EventDeliveryException that is unthrown
 -- make CounterGroup field final
Add TestRabbitMQSource

 -- add mockito to pom (managed upstream)
 -- add test-friendly constructors for RabbitMQSource
 -- add first test for happy path
 -- add log4j properties for test-only output
Add test for flume event headers
Fix rabbit-messages-unacked bug

 -- when flume fails to process the event generated by the source
    then the rabbit message should be nack-ed for retry
    otherwise the rabbit message can queue unacked forever

Also add counter for nacks.
Update README to add 'clean'

 -- probably helps to always rebuild from scratch!