argparse

• Simplify parsing numeric arguments with .scan #65
• Get arguments in optional with .present() #68
• Simplify a few internals #71
• Add the option to add text before and after help output #72
• Avoid use of cmd.exe in Travis #77
• Fix incorrect message when mUsedName is empty #79
• Make ArgumentParser::add_*() functions working on the parser itself chainable #82
• CMakeLists.txt : add export #86
• Fix help if required and def-value. Fixes #89. #90
• Show default value for arg in help message #92
• nicer usage text for required arg #93
• Qualify iterator functions #97
• misc clean ups #98
• Add Argument.append method to allow repeated argument use #99
• Add ArgumentParser.is_used to discern user-supplied values from defaults #100
• Allow user to limit version argument to --version #103
• Added packaging using CPack and generation of pkg-config files. #107
• Const-correct ArgumentParser #108
• Fix std::min conflict with min/max definitions from windows.h #109
• Replace size_t to std::size_t. #110
• Some cleanup in CPack packaging #115
• Document and use Argument.scan where possible #121