Display content based on request variables

There was a feature request to be able to nest shortcodes inside of
the existing shortcode `[switch]`. This is not possible without
overriding large portions of WordPress core. In speaking with that
customer, we came up with the content for `[block]`

[Addresses: GH-8]
Merge pull request #8 from gMagicScott/feature/block-shortcode

Nest additional shortcodes in `[switch]`