Changed compass Sass to use not as function.

This is "not" ideal, but it's necessary because of
https://github.com/sass/libsass/issues/368
Provided SassScript version of some Compass Ruby functions.
Updated Readme to reflect that some .scss files are changed.
Relocated sassscript functions to compass dir.

This location seems to provide a better API for imports, even if it
does intermingle our changes with Compass a bit.
Updated tests to reflect relocation of functions.
Merge pull request #9 from michaek/master

Change not to avoid libsass bug, provide some SassScript to replace missing Ruby functions