Add ability to change colors

[ntwcklng]

For example .colors({mainColor: 'red', subColor: 'bold' }) would output the commands and options in red, and the description in chalk.bold instead of chalk.dim

[leo]

Should be a config param, if you ask me 😊

[ntwcklng]

Yes! Should i create a PR? Would be nice if this gets merged before #63 gets merged.

[leo]

@ntwcklng yep! thanks 😊

[ntwcklng]

merged: f3a64cd