Merge pull request #26 from vhladama/improvements-and-fixes

Specs for PullRequestsData and some green-green refactors.
Merge pull request #24 from vaneyckt/improvements-and-fixes

update to v2.0
add travis ci badge
update gemfile
update gemfile
prevent possible bug when previous run left testing branch in unconvential state
Merge pull request #27 from vaneyckt/fix-edge-case-bug

Prevent possible bug when testing branch was left in unconvential state
remove unneeded &&
Make travis test some different ruby versions.
Add some more rubies to travis.
Add whitelist_branches method to ConfigFile.
Add support for whitelisted branches to PullRequestsData.