Fixes #43, #44, #45

Closes #43:

* Use `brew cask list` on the cask to determine if it is installed. If
  it not, the command returns a non-zero exit status. The `exitstatus
  == 0` will return true or false, so we don't need an `if` block.
* Additionally, the `not_if` aren't required since we are only
  configuring the resource if `@cask.casked` is `false`.

Closes #44:

* Add `:install` and `:uninstall` actions. For compatibility, `:cask`
  and `:uncask` use these respectively.

Closes #45:

* Add `default_action` method to set the default action if it's defined.
* Print warning messages that Chef versions less than 10.10, when
  `default_action` was introduced, will be unsupported in the next
  major release of the cookbook.
Closes #35, COOK-4679, modernize provider

This implements why-run mode and uses inline resources (if defined).
The other parts of #35 were addressed in e5fc6d8.
Obvious fix, closes #42

Also implement back compat default per my comment on #42.
Merge pull request #46 from opscode-cookbooks/jtimberman/cask-fixes

Fixes #43, #44, #45