v2.4.3: Auto merge of #500 - kbknapp:v2.4.1, r=kbknapp

v2.4.3 (2016-05-10)

Bug Fixes

• Usage Strings:
  • now properly dedups args that are also in groups (3ca0947c, closes #498)
  • removes duplicate groups from usage strings (f574fb8a)

Improvements

• Groups: formats positional args in groups in a better way (fef11154)
• Help:
  • moves positionals to standard <> formatting (03dfe5ce)
  • default help subcommand string has been shortened (5b7fe8e4, closes #494)