Adding minimal support for v2 API.
Initial commit of the v2 rewrite.
Currently only testing against cases (everything else is likely broken).
Added includes_key_chain to simplify checking for nested keys.
Fixed method_missing functions to support new .raw results.
Moved REQUEST_METHODS to a constant.
Test REQUEST_METHODS in respond_to for deashie to use.
Fixed access to some of the case items.
Cleaned up a bit.
Adding additional case functions.
Initial support for custom fields in Desk v2
Initial support for Labels in Desk v2
Add missing dependencies
Remove unnecessary variables to be used as return values
Add support to query inbound mailboxes using Desk v2 API
Update Inbound Mailboxes API endpoint that was mislead by dev.desk.com
Add support to retrieve a customer's ID based on response's self link
Fix a problem where results were not accessible on raw response
Use search endpoint when retrieving contacts with Desk v2 API
Retrieve ID's from entries extracted from raw collection result
Extract user ID from Desk v2 response's 'self' link
Support for new errors that the v2 version of the API may return

* HTTP 409: `Desk::Conflict`
* HTTP 422: `Desk::Unprocessable`
Add support for v2 API error messages
Validate new error messages support in specs