Font lock improvements

Now special symbols like `exit` and `clone` will not be highlighted when they occur inside other symbols. For instance, the word exit will not be highlighted in `my_exit_function`.

Also, function names will now be highlighted by the `font-lock-function-name-face` which before was unused. 

A symbol is considered a function name when it is followed by ` := method`

Variable declarations will also be highlighted with the `font-lock-variable-name-face`.

A symbol is considered a variable declaration when it is followed by ` := <something> `

before: 
![screen shot 2014-08-12 at 1 34 15 pm](https://cloud.githubusercontent.com/assets/1441728/3894698/11f3f290-2247-11e4-92a0-080a670c5178.png)

after:
![screen shot 2014-08-12 at 1 34 35 pm](https://cloud.githubusercontent.com/assets/1441728/3894701/17f03082-2247-11e4-80a3-ab1990cf42dc.png)