Add options hash / Add lower casing of key names

I want to integrate your parser into the NodeJS 'node-imagemagick' module (https://npmjs.org/package/imagemagick) because the parser in that module won't digest bogon input (as I receive it from graphics magick for a couple of test images) and is not very legible.

`node-imagemagick` likes to have the keys of the parsed Identify output lowercased, and the IMHO best way is to add that feature to your module.

I have added a unit test.
I have not added a test for combining lowerCase=true with camelCase=true, though it is possible to do.