Add CodeHeaderGenerator

Still need to refactor MakeCommand and MakeOptparse to use this new base class.
Convert make_command to use CodeHeaderGenerator
make_optparse now has header info
Update make_optparse tests
Update make_bash_completion tests
Update docs with make_optparse interface changes

Fixes #151
Add tests for CodeHeaderGenerator.
Merge pull request #172 from jrrideout/death-march

make_optparse now includes options for setting header information