Add git author environment variables to .travis.yml

Our specs execute git commands. When run in Travis CI, we were seeing
error messages like:

  *** Please tell me who you are.
  Run
    git config --global user.email "you@example.com"
    git config --global user.name "Your Name"
  to set your account's default identity.
  Omit --global to set the identity only in this repository.
  fatal: empty ident name (for
    <travis@testing-worker-linux-3-2-14691-linux-14-12347578.c45665.blueboxgrid.com>)
    not allowed

Setting the author name as an environment variable should resolve this
minor annoyance.

Change-Id: Iee2ed9308c69df868054156a05820de049afe1b9
Reviewed-on: https://gerrit.causes.com/29842
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>