Lyra 1.8.0

• Fix cmake version for deprecation of 3.5.
  -- Tomáš Slanina
• Remove some unused code in type traits compatibility code.
  -- Paolo Pastori
• Fix short option not using the option style for extracting value.
  -- Paolo Pastori
• Fix spec of help for arguments in main style help API.
  -- Paolo Pastori
• Fix various warnings in the most pedantic compile modes.
  -- René Ferdinand Rivera Morell
• Add example for option termination with arbitrary tail arguments.
  -- René Ferdinand Rivera Morell
• Fix short-option with value not being recognized when part of other short options.
  -- René Ferdinand Rivera Morell
• Fix error message when a required argument is not matched.
  -- René Ferdinand Rivera Morell
• Fix error message for sequence parsed arguments.
  -- René Ferdinand Rivera Morell
• Improve error message for parsing arguments in group, like commands, to better reflect user intent.
  -- René Ferdinand Rivera Morell