Remove vcr, webmock, and VCR cassettes

Currently, testing this admin app locally requires having a local instance of the API running. Therefore, it doesn't make sense to use VCR because the location IDs will be different for everyone. VCR stores the HTTP request in a cassette and reuses it instead of making a live API call. But if it doesn't recognize the HTTP request (i.e. it has different parameters than those stored in the cassette), it will raise an error.

This commit also consolidates the Warden login helpers into spec_helper and session_helpers
Style the accessibility checkboxes like the ones in categories
Strip blank values from keywords, service_areas, and urls

Before, if you added a valid URL and then clicked on "add a new website" and left it blank, it would create that empty website after clicking "Save changes."
Make category checkboxes dynamic to reflect current state

Before, we were using static html that was generated from the Open Eligibility hierarchy and with input values set to the category IDs returned by Ohana API. It wasn't looking up the current service's categories to see which ones it already has.

This commit refactors the cats2html rake task so that it generates dynamic HAML.

Other changes:
<label> tag is now on its own, like this:
```
<ul>
  <li class="depth0">
    <input id="category-emergency">
    <label>Emergency</label>
  </li>
</ul>
```
Before, the input was inside the label, which would cause the checking/unchecking to fail in Firefox.

Added code to the init() function to check on load if any checkboxes are checked, and if so, automatically reveal them.
Disable faraday-http-cache

No pressing need for it for now.
Minor README update
Forgot to include this file 3 commits ago