Update README (CommandLine.HelpFlag.Short part)
Update README (CommandLine.HelpFlag.Short part)

For this part of the README:

`kingpin.CommandLine.HelpFlag.Short('-h')`

go1.5 gives me: `illegal rune literal`

Compiled without errrors only this way:

`kingpin.CommandLine.HelpFlag.Short('h')`

Fixed corresponding part of the README.
alecthomas/kingpin