Add collection of /etc/network/interfaces.d for Ubuntu

Since 14.04 Trusty, ubuntu uses config scripts in
/etc/network/interfaces.d. Collect those.
Closes: #264

Signed-off-by: Louis Bouchard <louis.bouchard@canonical.com>
Merge pull request #265 from karibou/fix_interfaces.d

Add collection of /etc/network/interfaces.d for Ubuntu
Bring python 3.4 into the testing matrix

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
Allow failures for python 3.4 on travis-ci

Looks like python 3.4 is not ready available on travis-ci.org. We'll make
3.4 unit testing a requirement once travis-ci makes python 3.4 an available
environment.

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>