Add docstrings to Observable class

[jordandsullivan]

Issue Description

The Observable class lacks docstrings for most of its methods. While some might be considered self-explanatory (depending on a person's background), many are not, such as Observable.partition(). Even short @Property functions could still benefit from having fully written out explanations of what the property is.

Proposed Solution

Add descriptive docstrings for each method.

Additional References