Add basic support for default options
Complete the help
Make the model more powerful
Add support for implicit values
Merge branch 'master' into default_values

Conflicts:
	src/cxxopts.hpp
Cleanup
Fix warning
Revert change
Fix compilation
Fix implicit and short
Merge branch 'master' into default_values

Conflicts:
	src/cxxopts.hpp
	src/example.cpp
Enhance example
Finalize help
Fix warnings
Merge branch 'default_implicit'
Merge remote-tracking branch 'remotes/origin/master'

Conflicts:
	src/cxxopts.hpp