Added additional text markup detection.

- Added block quote detection (bq.)
- Added image link detection.
- Added horizontal rule detection.
- Ordered block macros to be detected before lists, otherwise the horizontal rule was detected as a bastardization of the list/strikethrough rules.

This takes care of everything listed on the [Confluence Wiki Markup][1] page except tables.

  [1]: https://confluence.atlassian.com/display/CONF53/Confluence+Wiki+Markup