Fixed Mocha for CoffeeScript 1.7+

`Gruntfile.js` and `test` are not currently compatible with CoffeeScript 1.7+ and they return the following error when executed:

```
Error: Use CoffeeScript.register() or require the coffee-script/register module to require .coffee.md files.
```

According to CoffeeScript's change log:

```
When requiring CoffeeScript files in Node you must now explicitly register the compiler. This can be done with require 'coffee-script/register' or CoffeeScript.register(). Also for configuration such as Mocha's, use coffee-script/register.
```

These changes fixes the error for when CoffeeScript 1.7+ is installed globally.

Also, https://github.com/hubot-scripts/hubot-example should probably be removed or edited to reflect the recent changes (Yeoman generator).