Pyding

Change log
* Added essential checks to `pyding.on` (see on [README.md](https://github.com/jaobernardi/pyding/README.md))
* EventCall.response will now have the last non-None return value.

Change log
* Fixed duplicate event calling in class events

Changelog:
* Added a better documentation using docstrings

Changelog
* Fix first response check for event calls.

Changelog
* Add `event.responses` to contemplate all responses from event calls

Changelog
* Changed how events are stored
Now events will be stored using the EventSpace object, allowing the existance of parallel scopes for events.

* `pyding.call` and `pyding.on` are now just 'proxies' to the global Event Space.

How Event Spaces work
An event space is just an isolated scope where handlers can be attached.

Example:
python
import pyding

myspace = pyding.EventSpace()

myspace.on("event")
def myhandler(event):
print("Hello world from myspace event space.")

This won't call myhandler since it is registered in myspace event space.
pyding.call("event")

This will call myhandler
myspace.call("event")
"Hello world from myspace event space."