Relelease Candidate 2.4.0.1

* Report SampleRate & SampleSource per updated SWIG API
* Change OboeHeroku __Init Key 
* Remove oboe_fu artifacts
* CodeClimate Initiated improvements
* Remove SSL connection requirement from Net::HTTP tests
* oboe.gemspec doesn't specify Ruby 1.8 json dependency
* add config to blacklist tracing of actions (thanks @nathantsoi!)
* Report the application server used
* Support Oboe::Config.merge! and warn on non-existent (thanks @adamjt!)

> git shortlog origin/prod..master

    Peter Giacomo Lombardo (46):
      Remove oboe_fu artifacts.
      Add version, build and climate badges.
      Merge remote-tracking branch 'origin/master'
      Slightly simplified get_multi_with_oboe method
      Cleaned up cache_get and request_setup methods.  Remove duplicated code.
      Moped instrumentation cleanup: better returns and exception handling
      Remove unnecessary duplicate block
      .try is a part of Rails and may not be available depending on stack
      perform and get_multi cleanup and refactor.
      Better method wrapper pattern.
      A better method wrap pattern.
      Fix block logic.
      Break out text copy to separate private methods.
      Updated SWIG from tracelytics/oboe#206
      Change keyname to RubyHeroku.Oboe.Version
      Include constants and accessors for bit masks
      Extract sample_rate and sample_source when available
      Report liboboe returned sample rate/source
      Include more liboboe constants and change r to rv
      On initialization, set all values manually
      Remove test for a default sample_source - liboboe handles that.
      Don't initialize sample_rate at all since it's not required in any case.
      Tests to validate SampleSource on localset
      Don't set sample rate/source manually.  Rely entirely on liboboe.
      Only report SampleRate/Source when tracing_mode == always
      Remove SSL connection requirement from Net::HTTP tests
      Updated ServiceArg test param
      Add json as a runtime dependency
      Merge pull request #14 from nathantsoi/master
      Detect Puma and/or Unicorn and report KV if found
      Detect Passenger, thin, mongrel[2] and Trinidad(jruby)
      Report more frameworks: Sinatra, Padrino, Grape & Cramp
      Merge branch 'net_http_tests_fix' into issue_9
      Remove duplicate gems to fix Ruby 1.8.7 warning:     
      Your Gemfile lists the gem rake (>= 0) more than once.     You should probably keep only on
      Re-enable Cassandra per:     https://github.com/travis-ci/travis-ci/issues/1650
      Downgrade Rubygems per: https://github.com/bundler/bundler/issues/2784
      Merge pull request #276 from tracelytics/issue_276
      Merge pull request #285 from tracelytics/issue_285
      Merge pull request #282 from tracelytics/issue_282
      Merge pull request #13 from appneta/net_http_tests_fix
      Merge remote-tracking branch 'public/master'
      Merge branch 'master' into issue_11
      Merge pull request #11 from appneta/issue_11
      Merge pull request #12 from appneta/code_improvements
      Merge branch 'master' into issue_9
      Merge pull request #9 from appneta/issue_9
    
    nathan (1):
      add config to blacklist tracing of actions