fix error when mbtiles path contains a space

root cause is that qs.parse() unescapes URL components while url.parse() does not.
https://groups.google.com/forum/#!topic/nodejs/8P7GZqBw0xg
http://nodejs.org/api/querystring.html#querystring_querystring_unescape
Add (failing) test for spaces. Refs #45.
Merge branch 'test-spaces' into space-in-path-fix
Merge pull request #45 from mapbox/space-in-path-fix

fix error when mbtiles path contains a space