Adding Literate CoffeeScript support for nodemon

Hello Remy,

CoffeeScript is currently in v1.6.2 and has had support for Literate CoffeeScript (`.litcoffee` extension) support since v1.5.0. I believe that adding support for Literate CoffeeScript for `nodemon` is necessary since the Readme indicates support for CoffeeScript in general.

This change will be a major benefit to the CoffeeScript community, whose transition to Literate CoffeeScript can be even more streamlined through using nodemon.

As you have mentioned in the Readme regarding testing, I've added a test/litcoffee directory  similar to that of test/coffee that demonstrates nodemon working with Literate CoffeeScript.

On test case worth mentioning is if the user attempts to run nodemon on a litcoffee file when their version of coffee does not support litcoffee. In this case, the coffee compiler will exit with a compile error, so it should be fine.

Let me know what you think about these changes.

Sincerely,

skaushik92