Added the click option to look for relay and transit urls in environment
variables. If you're running your own relay/transit servers (such as
inside a corporate firewall), this will make client's lives easier.
Tools which use `wormhole send` under the hood should use a distinct
--appid= (setting the same URL-shaped value on both sides, starting with a
domain name related to the tool and/or its author), so wormhole codes used by
those tools won't compete for short channelids with other tools, or the
default text/file/directory-sending tool.
Closes#113
So instead of "wormhole --verify send", use "wormhole send --verify".
The full set of arguments that were moved down:
* --code-length=
* --verify
* --hide-progress
* --no-listen
* --tor
The following remain as top-level arguments (which should appear after
"wormhole" and before the subcommand):
* --relay-url=
* --transit-helper=
* --dump-timing=
* --version
The values set by the base Config constructor could mask Click parsers
that weren't supplying defaults properly, or which were using different
defaults.
When tests need a Config object, they now call a function which invokes
Click with a mocked-out go() function, and grabs the Config object
before actually doing anything with it.
