MultipartKit 4.0.0 Beta 1

This library has been renamed to MultipartKit and rewritten on top of François Colas's streaming C multipart parser. This means its now possible to stream in large, multipart-encoded file uploads using very little system memory. Note that the form-data variant Encoder and Decoder still require the entire multipart payload to be in memory.

For some usage examples, check out the tests folder: https://github.com/vapor/multipart-kit/blob/master/Tests/MultipartKitTests/MultipartKitTests.swift