Fix some panic information when a 'catch-all' wildcard conflict occurs.

[blinklv]

    tree := &node{}   
    tree.addRoute("/who/are/*you", fakeHandler("/who/are/*you"))
    tree.addRoute("/who/are/foo", fakeHandler("/who/are/foo")) // Wildcard Conflict panic
    tree.addRoute("/who/are/foo/bar", fakeHandler("/who/are/foo/bar")) // Wildcard Conflict panic

The second one and the third one will throw panic, but the information is not what I want (Maybe I don't completely understand it). It likes below:

'' in new path '/who/are/foo' conflicts with existing wildcard '/*you' in existing prefix '/*you'

'' in new path '/who/are/foo/bar' conflicts with existing wildcard '/*you' in existing prefix '/*you'

I think below information are better.

'/foo' in new path '/who/are/foo' conflicts with existing wildcard '/*you' in existing prefix '/who/are/*you'

'/foo/bar' in new path '/who/are/foo/bar' conflicts with existing wildcard '/*you' in existing prefix '/who/are/*you'

So I change it. :)

[julienschmidt]

Thanks!