__eq__ implementation for Notification class

[azhou95]

The eq magic method for the Notification class seems to be implemented as a comparison of the two sides of the equality being casted to string.

This can lead to strange behaviour such as: OnNext(1.0) == OnNext("1.0") being evaluated as True.

Would it be possible to improve this behaviour?

[dbrattli]

You could try. Feel free to make a PR.