Fixes issues with simplecov + spork.

I needed to make some minor changes to the spec_helper.rb file and
restrict simplecov to the 0.7.x branch (there is a bug in the 0.8
branch that has yet to be fixed: https://github.com/colszowka/simplecov

I also took the liberty to update the Gemfile with Ruby19 hash syntax.
Merge pull request #5 from 18F/feature/fix_simplecov_spork_issues

Fixes issues with simplecov + spork.