option for cli project without git

https://www.pivotaltracker.com/story/show/49293849

Usage:

mmortar new my_project --withoutgit

or

mmortar projects:register my_project --withoutgit

unit-tests for this were a nightmare. FakeFS is buggy (went into infinite loops) and doesn't clean up properly when you use Dir.chdir inside of it, so I ended up manually making and deleting a tmp dir for some tests.

Do we need to update Rosie tests too?