[bug 1042222] update Vagrantfile to use 14.04 LTS

This updates the Vagrantfile to use the 14.04 LTS image instead
of 13.10 which has reached end of life.
Merge pull request #324 from lgp171188/1042222

[Bug 1042222] update Vagrantfile to use 14.04 LTS
Add L. Guruprasad to CONTRIBUTORS