0.4.0

Added

• Allow help messages colours to be configured (#7)
• Proof of concept of manpage generation (disabled in release as it's very incomplete) (#11)

Changed

• Changed default help message colour scheme to be more colour-blind readable
  and more visible on light and dark terminals (#7)
• Changed description of --help argument.

Fixes

• Remove superfluous style reset escape sequences (#7)
• Don't apply formatting to trailing spaces in argument names in help messages (#8)
• Print a readable error when the argument spec is invalid (#10)