v0.3.0

• Fully up to date with draft-ietf-httpbis-header-structure-13.
• Parameterized Lists and List of Lists are gone, their feautures are merged
  into List and Dictionaries.
• Both lists and dictionaries now require an object such as
  {value: x, parameters: y}. This is a breaking change, but was required to
  support parameters correctly everywhere.
• Stricter float parsing.