[feature request] ability to handle all methods

[bokunodev]

curently there is no way to bind a handle to all methods.
TreMux.Handle require me to specify the method name.

[dimfeld]

Due to the way the router works internally it would still have to add the handlers separately for each method, so it wouldn't really be any different from writing your own function to just do that but I'm fine with the idea.

That said, I'm not developing this package or even using Go anymore, but I'm happy to consider a PR if you'd like to submit one.