Fixing error in documentation

[cassava]

I noticed that there seems to be an error in the documentation; maybe you care to merge this fix?

[ogier]

That whole section of the docs is kind of crappy. The VarP example below that line is also wrong, that function doesn't take a default value and belongs inside a function not at top level. IMO that line should just be dropped entirely, VarP is pretty discoverable anyways.

[cassava]

True, the docs could be improved a little. Some of the text still applies (only) to the original flag package.

[ogier]

Do you have any examples of this? Ideally there shouldn't be any usage of the flag package that is broken by switching to pflag, so docs that describe how to create flags the old way don't only apply to the stdlib package.