Initial composition

This release is the first for raj-compose which is taking the raj/effect module and breaking it into its own project dedicated to program composition. This move away from core does a few things:

• Makes core smaller, and therefore more able to be stable
• Gives us a playground for experimentation with program composition
• Allows us to better document the functions (no one could tell what raj/effect did)

I've also made the APIs more strict and enforce plenty of invariants.