Use collections.abc.Iterable for type checking and flattenning

[sinewalker]

In Python 3.3, the collections.Iterable class was moved into its own module

Instead, now test the Abstract Base Class Iterable type.

https://docs.python.org/3/library/collections.abc.html

This fixes the error module 'collections' has not attribute 'Iterable' when calling methods such as minecraft.postToChat()

Fixes #68

[Greeniac]

Thank you, it works.