Add rubocop and rake task
Tidy up overly long lines
Use rspec eq() match rather than == comparison

Rubocop reports an error when using ==, so instead use eq() matcher.

In the process, move to rspec 3.0 expect().to syntax
Remove unused block argument for :publish_gem

(fixing Rubocop errors)
Remove useless private modifier

(fixing Rubocop errors)

This gives the impression that it is protecting
the class method after it, but private modifier only
protects instance methods.
Remove bogus @edge_gateways line

(fixing Rubocop errors)

This appears to be a typo, there is no reason to
specify @edge_gateway here
Include rubocop in default Rake task

So that CI will fail if lint checks fail.
Merge pull request #73 from alphagov/70748514_rubocop_and_fixes

[#70748514] Rubocop lint checking, and related fixes