simple parser for multipart MIME messages

 multipart-parser is a simple parser for multipart MIME messages, written in
 Ruby, based on felixge/node-formidable's parser.
 .
 Some things to note:
  - pure Ruby
  - event-driven API
  - only supports one level of multipart parsing: another parser needs
    to be invoked to handle nested messages
  - does not perform I/O
  - does not depend on any other library