Switch the generation of HTTP GET params over to the new, more
featureful method in Utils, which handles Rack/Rails style nested
parameters. Also add a variety of tests for this functionality.
If there is already a '?' in the URL, add additional query params using
'&' instead.
Ideally we would be more clever about this and actually take the URL
into parts and then unparse in a structured way rather than just blindly
appending, but oh well.
Fixes: #402, #96
* Put unit and integration specs into separate subdirectories
* Consolidate all requires of 'webmock/rspec' into spec_helper.rb
* Use WebMock.{disable!,enable!} for specs calling live server
