Update List Reg Ex to Avoid Order of Formatting Block Dependency

I noticed that if you were parsing Markdown such as:
```
**Strong Text:** Some Subtitle.

* List Item One
* List Item Two
```
the order in which the formatting blocks were called mattered. Everything worked fine with the standard parser, but if you ran your own custom parser, you had to specifically add the strong formatting block before you added the list formatting block. This PR changes the Reg Ex for lists to avoid this dependency.