Add support for method overloading

[exodrifter]

Add support for method overloading for bind methods.

For example, the following should be possible:

rumor.Bind("play", (string name) => {
    Foo.Play(Resources.Load<AudioClip>(filename));
});
rumor.Bind("play", (string name, float volume) => {
    Foo.Play(Resources.Load<AudioClip>(filename), volume);
});

However, Rumor fails with an ArgumentException

ArgumentException: An element with the same key already exists in the dictionary.