Support For Different Data Types

[4gatepylon]

I've tried to use this for floating point numbers and got a type error on line 403 for "mask = 1 << bit_within_wordno". It would be nice to support different data types such as floats by simply using the numerical values of the bytes (or some other mapping function specified by users).

[4gatepylon]

Added PR for a minimal implementation of this that allows users to specify a key function that will map their key objects to something filterable of their choice.