Adds missing options on sass_interfaces
[BUGFIX] Add fix for source-maps (Fix-Up PR #591)

- Remove line-breaks in Base64 encoded string
- Actually embed the source-map json in data-url
- Include original source in sources array
Merge pull request #619 from sass/bugfix/source-map-sources

[BUGFIX] Add fix for source-maps (Fix-Up PR #591)
Correctly handle nested feature queries