Few fixes and general cleanup

[kleisauke]

I've solved a few things and done some general cleanup. Also added some TODO's to make it working on Windows (all tests passes successfully on my Windows 64-bit PC after patching the DLL names).

Summary:

• Use the type-safe equality operators === and !== instead of their regular counterparts == and !=.
• Fix Image.prototype.band parameter.
• Fix unused local variables, unused parameters, unterminated statements, unused requires, redundant variables.
• Auto-indent lines.
• Add some TODO's to make it working on Windows.

Note: I'm not a Node.js expert, so maybe I overlooked things.

[jcupitt]

\o/