Merge tag '3.1.2' into develop

Relaxed gem dependencies; resolves #65
Minor changes to improve support for Ruby 1.9.3 tests
Resolves #57; ensures config is not overridden when initializing LiveStream
Relaxed version dependency on multi_json to resolve #67
Bump to v.3.1.3
Update Travis to test against latest Ruby 2.1 release
Merge pull request #70 from datasift/feature/3.1.3

Feature/3.1.3
Merge branch 'release/3.1.3'