Godoc update

Fixes a typo in the ServeMux godoc

Performance optimizations for Handle

Unrolls recursion in ServeMux.Handle

Fix issue with out of bounds panic on PathParameter

Fixes an issue where PathParameter was panicking if the n index passed to it was out of bounds and adds tests for those scenarios. Also brings us back to 100% test coverage.

Singular PathParameter

This changes the API so that instead of calling gemux.PathParameters(ctx) to get all the path parameters, you call gemux.PathParameter(ctx, n) to get the nth path parameter. If the path parameter isn't found, an empty string will be returned.

Initial development API release

https://semver.org/#spec-item-4

Note that the API should not be considered stable at this time, but I will still be following semantic versioning.