Gut the Makefile.

Didn't you hear? Cargo is the only game in town.
Say something about the convenient `exit` method in the docs.
Don't export the Value and Error variants explicitly.

The variants remain public (and there's no reason I see to change
that), but they are no longer exported as unnamespaced things mostly
because it's rare that you'll actually use them.

So imports like this:

  use docopt::{Docopt, Value, Switch, Counted}

should be changed to:

  use docopt::Docopt;
  use docopt::Value::{mod, Switch, Counted};

[breaking-change]
0.6.9