Multipart provides a parser for the multipart/form-data format. It can read from
a file, a socket or a WSGI environment. The parser can be used to replace
cgi.FieldStorage to work around its limitations.

Features:
- Parses multipart/form-data and application/x-www-form-urlencoded.
- Produces useful error messages in 'strict'-mode.
- Gracefully handle uploads of unknown size (missing Content-Length header).
- Fast memory mapped files (io.BytesIO) for small uploads.
- Temporary files on disk for big uploads.
- Memory and disk resource limits to prevent DOS attacks.
- Fixes many shortcomings and bugs of cgi.FieldStorage.
- 100% test coverage.