Flag constructor arguments order isn't consistent with Option

[robertjpayne]

The Flag constructor takes default as the last argument where as Option takes it as the second argument.

When using both in a single command it's a bit weird to have:

Flag("web", description: "Whether or not to search the web", default: false),
Option("remote", "cocoapods.org", description: "Custom remote host"),

[kylef]

The arguments have been aligned in Commander 0.8.0.