Decode local files paths

This fixes an issue where the absolute path to the stylesheet contains a
space. `url.parse` encodes spaces as `%20`, which won't be readable by
`fs.readFile`.
Sanitize destHref with 'file:' protocol and starting with '/'.

related issue: https://github.com/joyent/node/issues/5452
Merge commit 'ca10679293c425a7c1594dcc70d4f697a5042094'
Merge pull request #77 from antoniodots/master

Sanitize destHref with 'file:' protocol and starting with '/'.