Refactor to have cli directory.

[jangsutsr]

First step towards transferring Tower CLI from CLI to CLI + Python lib.

[coveralls]

Coverage decreased (-1.2%) to 89.549% when pulling 72cf8d4 on jangsutsr:refactor_to_have_cli_dir into fb6540b on ansible:master.

[AlanCoding]

In the release notes of the version this goes out in, I want to specifically call out the deprecation of as_command, and note the new class for subcommands. Also, specifically note that get_resource will continue to work as usual (this should be the most common use pattern).

Those have some risk of impacting people who have built off of tower-cli, but I think it's sufficiently small, and I'm good with shipping this.