Attempt fix Travis CI using OTP 17

[lucafavatella]

Please refer to commit message for details.

Sample output of last (failing) Travis CI build:

...
==> lager (compile)

ERROR: OTP release R16B01 does not match required regex 17

ERROR: compile failed while processing /home/lci/lincx/deps/lager: rebar_abort

Connection to erlangonxen.org closed.

The command "ssh -tA -i id_rsa -o StrictHostKeychecking=no -o CheckHostIP=no lci@erlangonxen.org ./lci $TRAVIS_COMMIT" exited with 1.

Done. Your build exited with 1.

[lucafavatella]

I did not manage to test this PR before submiting it as it looks like the Travis CI configuration accesses another machine via SSH, and I am not sure how to reproduce the setup of that machine.
Is there a script for setting automatically a box as the one the Travis CI config accesses via SSH?

Edit: I found https://github.com/FlowForwarding/lincx/blob/master/docs/testbed-setup.md but it relies on dedicated hardware and it is pretty manual (not automated).

[lucafavatella]

CI fails because of http://docs.travis-ci.com/user/pull-requests/#Security-Restrictions-when-testing-Pull-Requests