Ignore *.axd Routes

This commit is not the most DRY way of fixing the problem, but I noticed that HotTowel simply builds on top of the OOTB templates without changing them, so this is keeping with that strategy.

This commit will allow for *.axd files to be served from HotTowel applications without user changes, which will help to support [Glimpse](http://getGlimpse.com), [ELMAH](http://code.google.com/p/elmah/), [Cassette](http://getcassette.net/) and a host of other open source projects.