Moved all salt-cloud files into a subdirectory for move to Salt

This is the simplest method of preserving the commit history for each
file from the salt-cloud repository, although the --follow flag must be
given to git log in order to view the full history.

This change allows for performing a regular git merge from within the
Salt repo without any merge conflicts occuring (since the salt_cloud dir
doesn't exist there).
Added README with deprecation notice, links, and FAQ on the move
Merge pull request #896 from whiteinge/salt-move-and-notice

Salt move and notice