use ruby comments instead of html comments

i [prefer][x] commenting out my code with `-#` instead of `/` because it doesn't render anything (no `<!-- ... -->`) and it doesn't execute any code that nested below it.

this is a pretty lame PR as it breaks syntax highlighting for `/`. syntax highlighting for `-#` *should* grey out everything nested below that line too. if editing regex in cson files didn't make me want to die i would fix that. that said, i find this more usable than `/`.

[x]: https://github.com/schpet/language-haml/commit/9c4c4dd7d12515771ece6b0cde1a600bbc53ab14