In docs, move commas out of code

The commas separating these keywords are not code themselves – not what the user would write – so they should be outside of the `<tt>` tags.

Edits the table in the section [Operators and Aliases](http://coffeescript.org/#operators).

Before:

![portion of the operators table before my change](https://f.cloud.github.com/assets/79168/2026104/7bb34a3a-8889-11e3-8d2a-cda58a194f28.png)

After both commits:

![portion of the operators table after my change](https://f.cloud.github.com/assets/79168/2026156/c3d8215e-888a-11e3-9874-a45ada1ccd67.png)