Swift 3.0 Beta Seed 6

[Bersaelor]

My team and I were interested in Lyft/mapper as a replacement for ObjectMapper and we needed it to work with swift3 beta 6.

This is just a proposal that makes the tests succeed, but may not be the best solution.
Some method parameters should be adjusted to fit the spirit of the 'Grand renaming' more closely.
For example this method that could be renamed to:
JSON(from field: String) so it would read let result = JSON(from: string)

Furthermore we need to be aware that a 'var some: Any' can now be downcast to 'AnyObject' everytime, like here.

[keith]

Hey @Bersaelor thanks for submitting this! We've actually merged #75 and a few other changes to keep it up to date. Please track #76 for progress!