Refactor code, split out maths to firemath.py

Instead of doing all of the math in firemarshal, use a module to keep
thing separate. This way it can be re-used in other systems if need be.
Add argument parsing

Also disallow being loaded as a module.
Improve help output, use multiline strings
Merge pull request #3 from KaiSforza/modules

Refactor code, split out maths to firemath.py, add arg parsing