Path names are not escaped

[oweidner]

If the path to gpm's working directory contains white spaces, I see the following errors:

>> Setting github.com/mattn/go-sqlite3 to version 
/usr/local/bin/gpm: line 66: cd: /Users/codewerft/Codewerft/Kunden/03: No such file or directory
/usr/local/bin/gpm: line 66: cd: /Users/codewerft/Codewerft/Kunden/03: No such file or directory

The working directory in the case above was /Users/codewerft/Codewerft/Kunden/03 - XYZ/Entwicklung/reactor.backend.

[pote]

Huh, we were careful to escape paths early on to avoid this, but it seems somewhere along the way we refactored the cd step and forgot about it.

I'll fix it and make a release soon. :)