Add HTML renderer built on ParserObject

[dominickpastore]

Note: At the time of this issue's creation, much of the code mentioned below isn't yet in the repo, but it will be soon.

The DOMParser by default produces a DOM that is capable of producing HTML. This is great for users that need to do some DOM manipulation and then output to HTML.

Currently, subclassing the DOM object is also the only way to customize the HTML output if HTMLRenderer doesn't produce the results you need. If you do need that but don't need DOM manipulation, DOMParser adds a lot of overhead you don't need.

It would be useful to add another subclass of ParserObject that does HTML rendering without producing a DOM. Then, for the use case in the previous paragraph, a user can just subclass this new class and override methods as appropriate.

[dominickpastore]

Make sure to update the "Advanced Manipulations" section of the "Generating HTML" page in the docs after implementing this (and perhaps rename that section to "Advanced HTML Generation")