fontello executable and remove rails dependency

[bumi]

this adds a fontello executable and makes the rails dependency optional.

you can use it to edit a config file:

fontello open -c /path/to/config.json

or to convert a downloaded zip file:

fontello convert -i /path/to/download.zip -s /stylsheet/dir -f /fonts/dir

[bumi]

not sure if you get a notification via email, so: ping @jhilden @paulwittmann

[jhilden]

Awesome!

You will need to explain some of the details to me though and we need to update the README before it can be merged.