Add support for an options object

[lokesh]

• Update the getColor and getPalette methods to support an options object as their second parameter.
• If a numeric value is passed as the second arg, then it should fall back to using that as the quality option.

The creation of the options object will set up the library to add other features such as:

• Return format (rgb or hex)
• Area to sample (specify a portion of the image to sample)
• Ability to toggle off the white/near-white and black/near-black exclusion
• et al