Stub save_token to avoid overwriting valid tokens.json file

Fixes #22
List all apps via "aptible apps"

Closes #34
Add --port option to "aptible db:tunnel"

Also, rename tunnel to "db:tunnel" and move to a new subcommand class

Fixes #29
aptible db:dump

Fixes #30
db:create functionality, without --source

Closes #33
Fix arguments for SSH
Add db:clone functionality

Closes #39
Depends on aptible/sweetness@07d22401887617f1c32cfa17c592ec9f33bbe39c
Depends on aptible/api.aptible.com#83
Rubocop fix
Bump minor version due to breaking changes (tunnel -> db:tunnel)
Merge pull request #38 from fancyremarker/fourchette-flow

Some tools related to an app-per-branch workflow