Added support for (optional...), using "of" and splitting ingredient and action

This is a great little gem, and I just wanted to contribute my additions upstream. I have added support for the following new elements in an ingredient line:

```
(optional, if you have it at hand) 1/4 c. of white wine
3 cups of russet potatoes, cubed
```

As you can see, ingredients now support the usage of the word "of" as well as extracting the `optional` clause and separating out the actions that are needed for a specific ingredient.

What do you think?