tweaks to make libsass compatible

these are just syntax/formatting fixes that libsass chokes on - interesting to note:

1) base64 encoded images must have no whitespace (makes sense)
2) no semicolons after style blocks (hard linting, which is good)
3) the Ruby/Sass `not` operator is a function, and should not have a space before the parens (to be safe - it appears that it does work when you only have one boolean expression, but libsass doesn't seem to treat it like the python `not`).

Amaze.