Improve Feature Spec Coverage

:construction_worker: 

This PR aims to accomplish two things:

* Make sure the feature specs not ending in `_spec.rb` now end in `_spec.rb`. They were not getting run, and some were not passing. This gets them passing and gives them the right file name.
* Improve the feature spec coverage surrounding the Contribute views in Supermarket:
  * viewing contributors of a CCLA organization
  * permissions for accessing and viewing CCLA organization management views
  * reaching various pages and flows