docker-osx-dev crashes if current path has a space in it

[seanhuber]

I tried running docker-osx-dev in a directory that has a space in its name and it failed with:

2016-06-29 22:27:38 [INFO] Initial sync using tar for /Users/seanhuber/Rails
tar: Rails: Cannot stat: No such file or directory
tar: Error exit delayed from previous errors.
2016-06-29 22:27:38 [INFO] Initial sync using tar for Apps/rt_treats
tar: could not chdir to 'Apps'

tar: short read
error in run: exit status 1

The path of the directory I was in is /Users/seanhuber/Rails Apps

[brikis98]

Seems similar to #102. Probably a path somewhere isn't quoted. PRs welcome :)