Release version 2.5.0.7

# oboe 2.5.0.7 (02/13/14)

* Added new Redis redis-rb gem (>= 3.0.0) instrumentation
* Fix a SampleSource bitmask high bit issue
* Expanded __Init reports
* Fix Ruby standalone returning nil X-Trace headers (1B000000...)
* Test against Ruby 2.1.0 on TravisCI
* Fix errant Oboe::Config warning