add ability to tab paragraphs in rift docs

[lukehmcc]

Basically I think the ability to put in four   keycodes automatically after hitting the tab key would be great.

Also I do think that being able to customize the amount of spacecs per tabs would be great.

[alexfreska]

I have support for a literal tab currently commented out as I have not thoroughly tested its implications on other tab-based behaviour. I will make sure to look into rendering it with tabs vs spaces when I go to complete the feature.