allow getting/setting the include path
expose the fact this is a fork to userland

next step will be to update sacy to use this extension and I want to
make sure there that the correct extension is being used (of sensational
flavor)
allow getting and setting the image path
bring return values in line with PHP standards

failing functions are more or less always returning false, not NULL
change tabs to spaces

I'm really sorry. The original project hasn't been updated since a year
and I'm fully intending to maintain this alongside sacy, but only if I
can have files without tabs to work with :p
update version
update tests for new interface

also note that there's something fishy in libsass. The test.scss that
was provided originally produces different output when compiled by
libsass than when compiled via the ruby compiler

This was already the case with the initial file (@import should all be
moved to the top).

Now as the test.scss as provided didn't really make sense to begin with,
I've reduced it to something that actually compiles correctly.

This is about testing the PHP extension, not libsass
updating docs as needed