Documentation lacks many internal links

[multani]

The documentation is really good, but there are lot of references to other objects returned or used internally which are missing, example:

• https://rabbitpy.readthedocs.io/en/latest/simple.html#rabbitpy.simple.get doesn't get the return type right
• https://rabbitpy.readthedocs.io/en/latest/simple.html#rabbitpy.simple.publish has no link towards Properties
• https://rabbitpy.readthedocs.io/en/latest/api/channel.html : the intro text only has a good reference towards Connection.channel() etc.

I had a look and many links are broken because either:

• it references the imported class/function in the __init__.py module and this module is currently not processed by Sphinx (not automodule defined)
• it references the correct fully qualified name which is also not processed by Sphinx

I'm willing to send a patch, but it will probably require to use fully qualified names everywhere instead of using the shortcuts provided by the __init__.py module. Would that be OK?