Support Gemfile dirs with spaces in the name

[kopischke]

Without this, grep will choke on Gemfile directory paths containing spaces, spewing “no such directory” messages.

[aripollak]

Thanks for the patch; would you mind also adding a test for this?

[kopischke]

Changing the test to work in a dir with a space in its name should do it. See second commit.

[aripollak]

I think it would still be nice if there were an explicit test for it, so it doesn't accidentally break later.

[kopischke]

You may be right, but I won’t be writing it, as learning your test framework would take considerably more time than I have available for this (sorry if that sounds harsh, but that’s how it is). Considering how trivial the code change is, that it cannot have negative side effects (as the behaviour of quoting file paths in the shell is unambiguous) and that it fixes a show stopper, maybe merge the patch and just put extended test coverage on your todo list for the project?