Slow parsing with inline HTML on 0.4.14

Converting a document with a certain amount of inline HTML is very slow. The original document contained way more content than just the `

` tags, thus resulting in even higher conversion time. I stripped it down to just the inline HTML in order to ease reproduction.


I created a [gist](https://gist.github.com/mrreynolds/7319603) for the mentioned document.

``` bash

$ peg-markdown -v

peg-markdown version 0.4.14

Copyright (c) 2008-2009 John MacFarlane.  License GPLv2+ or MIT.

This is free software: you are free to change and redistribute it.

There is NO WARRANTY, to the extent permitted by law.

$ time peg-markdown document.md

[OUTPUT STRIPPED]

real    0m4.217s

user    0m4.202s

sys 0m0.009s

```

Suprisingly, plain old Markdown is pretty fast at converting the document:

``` bash

$ time markdown document.md

[OUTPUT STRIPPED]

real    0m0.049s

user    0m0.042s

sys 0m0.006s

```