Pass -q to svn in Downloader
Support specifying commit IDs in VCS URLs (Closes #36, #43)

Curdling now supports specifying a commit ID in the VCS URL. The user
can do that by suffixing the URL with a `@` symbol and the revision
ID. E.g.:

  $ curd install git+http://domain.com/project.git@81a57...ca05