Add components-a?rgb with tests

Hello,

I wanted to visualize a PRNG this morning and found imagez. It's great!

I noticed that `components-a?rgb` were unimplemented, so I decided to whip up a simple implementation.

The docstring said that the functions would return doubles, but it seems more in keeping with the rest of the library to simply return longs, the return type of bit-ops on long inputs.

Thank you!