Documented the text roles

[troublemagnet]

Added the custom text roles section to sphinx-specific markup.
closes #113
closes #108

[adammichaelwood]

Please do not do mass find-and-replace on a document. Ever.

• There was no need to change the code-block language designations from rest to rst
• Even if there was a reason, this PR was not the place to do it.
• You caught the actual word "rest".

The role content itself is fine.

• The issue Form states #113 specified an addition to custom.css, which is not included.
• You do not need to change all the code block language declarations back at this point. However:
  • Please fix the places where the word "rest" (or other words) got mangled.

[troublemagnet]

@adammichaelwood Sir the class style is already there in custom.css and I'm really sorry for the mass finding and replacing sir, I'll never do it again.

[adammichaelwood]

Thanks. Good work.