Peter M. Groen / cxxopts

Fixes #102. Don't show the default value when it is a boolean and the
value is false. Note that this is a bit of a hack and the
implementation should probably be reevaluated in the future.

Fixes #72. This adds an option for positional arguments to be
shown in the help output.

This is far from ideal, but it's the first step in moving the parse
result to an immutable object so that the parser can be reused.

Adds generic parsing of types using `operator>>`, in particular allows
parsing of floats and doubles.

Fixes #57.

Allows spaces after the comma between the short and long option
specification.

Conflicts:
	src/cxxopts.hpp
	src/example.cpp

Conflicts:
	src/cxxopts.hpp