Use Travis previous image version of Trusty
Use Travis previous image version of Trusty

Tests failed when Travis updated their Trusty environment. See https://blog.travis-ci.com/2017-12-12-new-trusty-images-q4-launch

To do - Make changes to enable it to run on the new environment - 
This change will be needed in requirements.txt
'''psycopg2==2.7.3.2'''
This removes one error. Full impact of this needs to be tested.
Two tests will still fail, see build #524
pontikos/phenopolis,pontikos/phenopolis,phenopolis/phenopolis,phenopolis/phenopolis,pontikos/phenopolis,pontikos/phenopolis,phenopolis/phenopolis,pontikos/phenopolis,phenopolis/phenopolis