withSort does not sort properly

I could not get withSort working, so I fixed it.

returning the value of comparison is not a proper way to do sorting. Instead one should return one of these values: ```-1```, ```1``` or ```0``` based on sorting order.

Note: this bug has also been fixed in assemble/handlebars-helpers#29 but I fixed it here too in case this might be accepted quicker
Added sorting support into coffeeScript of withSort too

Here's the coffeeScript version with fixed sorting..
Merge pull request #34 from Arkkimaagi/patch-3

withSort does not sort properly