Add pgbackups:transfer

This pull request migrates the pgbackups:transfer functionality from pg-extras
into the main Heroku CLI
also rescue this timeout on heroku run

see #1039
do a direct transfer for the app pg backup on fork
clear forked apps on error
Merge pull request #1041 from heroku/fork-tweaks

Fork tweaks
Release v3.4.0

Add pgbackups:transfer, for direct database to database transfers
Use app::color-style prompt for psql
Improvements to Heroku Fork
v3.4.1
Protect against funny business in attachment names
Fix pg:psql prompt quoting on windows
Warn user when log channels drop history.

Certain channels get flagged into this due to excessive output; this
will alert the user that this has occurred.
Merge pull request #1043 from deafbybeheading/fix-windows-pg-psql

Fix windows pg:psql
v3.4.2
update gemfile.lock
Read general-purpose warnings from tail sessions.
Actually handle errors in log tailing.
Merge pull request #1044 from heroku/log-history-warning

Log history warning
v3.4.3
do not try to fork to the same app
confirm before deleting app
Use standard confirm_command to check app name in confirm