Few minor tweaks and addition of spec folder

Hey Ben,

I've added a few tweaks, please see the summary below:

* Added spec folder with initial unit tests for Intervention module and added placeholder for proxy and transaction    files.
* Tidied up the Gemfile and .gemspec - removed gems for Gemfile already defined in .gemspec, added coveralls, added initial versions of gems in .gemspec and added Gemfile.lock to .gitignore. 
* Remove require for 'bw_intervention' - didn't think was needed and was left over from funky friday.
* Updated version and date.

Please note that I noticed that the gem wouldn't currently work for versions 1.9.2 and 1.9.3 due to the keyword arguments passed in the new_proxy method. Depends whether you want this to support other ruby versions but might be good to try and support at least 1.9.3? Upto to you.

Hope you don't mind me sending this pull request, want to start contributing to repo's and thought this would be a good one to start with! :bowtie:

Cheers,
Jon