New Extensions and Modifications

These extensions were just for fun, but I actually like using them.  Feel free to reject any you don't think we need.

### Insert Extensions
Use `^^test^^` notation to get <ins>test</ins>
You can now escape the `^` character as well.

### Modified Delete Extension
You can now escape the `~` character.

### Admonition Icon Extension
Adds an icon span to admonitions that can be styled with CSS.  Default CSS uses a stripped down font-awesome

![screenshot 2014-07-27 15 02 06](https://cloud.githubusercontent.com/assets/1055125/3715136/52ca4dc8-15d1-11e4-82e8-bb42088ab238.png)

Also if admonition class is not recognized, it will be styled in simple gray.

# Progress Bar Extension
Allows the creation of a progress bar with the following notations:

- Percentage: `[== 35% optional label]`
- Division: `[== 37.5/500 optional label]`

Default styling is a flat candy-striped  bar, but there is included CSS for animated candy-stripping and a glossy bar.  You can access one or more of these additional stylings by adding the classes when enabling the extension `progressbar(addclasses=candystripe-animate gloss)`.  Also by default, progress bar extension adds classes to allow for different stylings of 0-20%, 21-40%, 41-60%, 61-80%, 80-99%, 100%.  This can be turned off by defining the extension as `progressbar(levelclass=False)`.  Additionally you can change these settings with this inline notation `[==50%  MyLabel]{addclasses="additional classes" levelclass="false"}`.  When level classes are disabled, the default color is blue.

![screenshot 2014-07-27 15 12 37](https://cloud.githubusercontent.com/assets/1055125/3715155/c52886fe-15d2-11e4-9122-8051571c81e4.png)

### Other
- Selection is now blue and doesn't conflict with mark tag highlighting.
- Caution admonitions are now orange and notes are now yellow.
- Test file has been updated.