Allow case-invariant urls

Currently

https://www.nuget.org/packages/log4net.GrowlAppender/ returns a 404 while
https://www.nuget.org/packages/log4net.growlappender/ works (even though I named my project with PascalCase).

It was a minor annoyance in that I had published a nuget package referencing the url with the PascalCase and had to go update my package and increment a patch version number just to get the url to resolve.

Perhaps you disagree, but I think that this breaks a common web convention for case insensitivity in urls