Fix test: bundle exec git-pretty-accept.

Ensure spec picks up the local git-pretty-accept binary.
Force push PR branch when rebased.

So that merging to master will automatically close PR in Github.
Update gems for Ruby 2.0.

* Remove debugger.
* Remove rake version.
Add pry.
Specify branches when pulling from and pushing to origin.
Abort script if branch being merged is master.

* Use log commands instead of puts.
Merge branch 'improvements'

* Specify branches when pulling and pushing to origin.
* Abort script if pull request branch is master.
* Replace debugger with pry.
* Ensure that the `git-pretty-accept` call in the tests is using the latest
  version of the gem.
Bump to 0.1.3.