Use optionator for option parsing, not optimist - for #596

Optimist is now deprecated, this commit changes option parsing
and help generation to be done with [optionator](https://github.com/gkz/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.

In the future, you could add `longDescription` and `example` fields to all the options, and use `generateHelpForOption` from optionator to display more detailed help for an option when you do `--help option-name`, and even generate your options documentation automatically from the options specification object - [Grasp](http://graspjs.com) does these things.