use optionator for option parsing, not optimist

optimist is now deprecated, this commit changes option parsing
and help generation to be done with optionator.

Tests are simplified in that they now can pass in a string of arguments,
just like on the command line, instead of an array of strings.

Options are now accessible through the option's full name.
Eg. `currentOptions.help` instead of `currentOptions.h`

A lengthy comment labeled TODO is gone since it is no longer an issue
when using optionator.

The responsibility of printing the help text to the console is given to
cli.js instead of options.js, which I feel is more appropriate.