Deprecate async apis. Fixes #70

This PR is the cherry-pick of [#76](https://github.com/jclouds/jclouds-chef/pull/76). The PR was made for 1.6.x, and this commit brings the changes into master:

* Deprecated all async apis.
* Refactored tests to extend BaseApiLiveTest.
* ChefContext now extends View.
* HostedChefApi now extends ChefApi.
* PatchedChefApi has been removed.
* Removed HostedChefContext and PrivateChefContext because they are now
  redundant. The concrete apis can be unwrapped from teh ChefContext
  view.