Use WebMock to mock response for successful connection when configured.
Raise ConfigurationError when missing requried config client_id, secret.
Reset webmock stubs; configure zoning in all connection specs.
Remove rails-only methods; response is invalid if key not found in response.

* try, present? are not in ruby stdlib
* In Connection#parse, use Hash#fetch to raise exception when key not
  found.  This is then rescued and "Invalid json response" is returned.
Specs for Zones#list

* Spec for when the response is something unexpected
* Checks the key is accessed
* No subdomain results in []
Store access token in Configuration, clear config before specs.

* Allows the access token to be persisted and set by some user of the
  zoning gem.
* Reset all config before each spec to ensure true tear up / tear down
  between each spec.
to_query must be called explicitly when using Faraday like this.

Other option is to depend on a core extension from active_support
Validate search parameters for the Zoning endpoint.

Validation for search endpoints consists of adding two lines to the
endpoint module:

* Define `ALLOWED_SEARCH_PARAMS`, which is an array of symbols that can
  are valid search keys for the model.
* Add `prepend Zoning::SearchParamsValidator` to the module.

If we want more validation across other methods, this should be fairly
simple by modifying the validator to inspect the class & __method__ and
pick the correct validator from there.
Constant declaration moved closer to #search method, replaces comment.
Support in the validator for #search with only query param.

This is a bit ugly. If we want more validations, or are willing to
adjust the API slightly it might be worth changing the approach.
SearchParamsValidator specs in one file; repeat for other endpoints.
Allowed search parameters for endpoints now in parity with ZoningAPI.
Style - Reduce whitespace between methods.
Fix specs; remove no-longer-valid search params from specs.
Correctly fail when #search given no parameters.

At least one argument is required - the subdomain.
Merge pull request #3 from opencounter/tests

Tests