Partially fix passing environment through to SSH mode

Dropbear doesn't have a facility to add arbitrary environment to client
processes; fix /etc/profile workaround to work at least for shells.
Merge remote-tracking branch 'koterpillar/ssh-environment'
Release on Python 3.4
Add python3 and python3-pip pre-reqs
Revert dupe comment about python3
Update README.md
Show the output of Pylint
Update Docker package
Merge branch 'update-docker'
Add PostGIS container rather than just bare bones postgres
Make container image a class constant

Syntax error
Merge remote-tracking branch 'origin/postgis-container'
Before returning service available, make sure port is connectable
Pylint fixes
Use port_open instead of raw socket
Pull out container start from ensure_container
Split out waiting for a port to become available
When starting Postgres, wait until it's available before return
Fix PostGIS CHECK_COMMAND
Pylint fixes