doc: add documentation for errors

This adds documentation around what errors are generated by Node and how to intercept them.

The rendered docs are available [here](http://neversaw.us/nodejs-api/errors.html).
> If it cannot, it simply displays location information for that frame. If it can, it will display the name, and put the location information in parentheses.

Too many commas and "it"'s. Be more explicit. Proper noun redundancy is better than confusing usage of pronouns. For example:

> If no function name is found then the frame will only display the location where the function was executed. Otherwise the function name will be printed followed by the function execution location wrapped in parentheses.