Lossy compression added

AIS is meant for maintaining a real-time display, so that you don't hit other ships. That means for other uses, there's a lot of pretty-much-redundant information. This library now includes the aisrefine tool, which will take a large file and perform lossy compression. At a minimum you'll see one AIS sentence every four hours from a sender, and more if the ship significantly changes things like speed, destination, course, or draught. This provides circa 96% compression on large files, and was a much easier way to speed up the library than rewriting everything in C.

Release available on PYPI: https://pypi.org/project/simpleais/