Cannot specify location of sassdoc in gulpfile

[kamsar]

When integrating Phoenix with other projects, it's a bit awkward that by default it emits the sassdoc hardcoded to ../../documentation/sass-api from the driver. Everything else goes in dist, why not sassdocs?

[elseloop]

As we're currently working on a rewrite/rethink of our build system, I'm pushing this onto that work. Keeping it open, though, so it remains a concern.