Travis CI file installs and runs tox
Travis CI file installs and runs tox

This way, Travis CI config file contains instructions how to install
tox on Travis Ubuntu machines and which tox enviroments to run there.

Based on Travis CI documentation[1]:

> To install Ubuntu packages that are not included in the default
> standard, use apt-get in the before_install step of your
> .travis.yml:

[1] https://docs.travis-ci.com/user/installing-dependencies/

tendrl-bug-id: Tendrl/node-agent#235

Tendrl/node-agent,r0h4n/node-agent,Tendrl/node-agent,Tendrl/node_agent,Tendrl/node_agent,r0h4n/node-agent,Tendrl/node-agent,r0h4n/node-agent