Added null check to TupleToJsonStringConverter
XD-790 - Fixed System.exit() test issue
XD-793 Upgrade Spring Data Redis to 1.1 RC1
XD-789 Add index-access for Tuples

+ check for negative index
XD-792 Use SI twitter search support.

TwitterSearchMessage source was a temporary fix to provide
authenticated twitter search until it was supported by Spring
Integration.

However, we still need a customised versions of TwitterTemplate
which can be configured with the consumerKey and consumerSecret as
Spring Social doesn't provide a matching constructor which will obtain
an OAuth2 bearer token internally.