Exclude URLs from processing

This adds the ability for the module to exclude URLs matching a Regex from being processed. I am using this to prevent the Glimpse.axd files from being processed, as the i18n module currently breaks Glimpse.

In addition, you can add ?i18nSkip to the URL and you'll see your original page without the nuggets being processed. I find this very useful for
- checking how I've defined my nuggets, particularly those that make substitutions
- some admin screens where I define nuggets that are stored in a database

I'm afraid this is my first ever pull request on GitHub so I'm not sure if I've done it right, of if this is even welcome!

Also there are a load of other changes I made but have reverted - but I can't get rid of the trace of them.