Upgraded Ubunutu to 14.04

This commit:

upgrades:
  - the ubuntu image to 14.04 Trusty Thar
  in the base image:
    - phantomjs to 1.9.7
    - ruby to 2.1.6
    - gradle to 1.12
fixes:
  - a bug which caused the java installation to fail #17, #20
- changes the default user to root
- changes the home directory to /root