Added Cucumber <-> VCR integration

* All Cucumber features are now VCR-enabled and recorded.
* When adding a new feature, you HAVE TO tag it otherwise
  the tests won't pass! See 'features/support/env.rb' for
  available VCR tags.
Fixed VCR integration with Cucumber

* Using a patched version of VCR 2.4.0
* Removing slashes from cassette names
Updated RSpec tests

* Fully integrated with new VCR using metadata
* Standalone cassette for every testcase
* Updated VCR patches
Fixed should_*_compute_resources cassettes
Updated RSpec tests

* Renamed misleading test names
* Replaced TODOs with proper "pending" status
Updated RSpec tests II.

* Tests should state what is going to happen, not what
  should happen ...
* A few additional ClientHttp tests
Fixed get_entity_type* docs
Updated RSpec tests III.
Merge pull request #41 from arax/client-dev

Added Cucumber <-> VCR integration