integrated boost::program_options.

will now accept options to display in MiB or KiB, default remains GiB.

most errors are caught gracefully now thanks to try and catch.

cgb --help or cgb on its own will now display built-in help.
Update cgb.cpp

removed old commented code no longer needed as a reference
Merge pull request #2 from dryack/integrate_boost_options

Integrate boost options