Merge pull request #13 from ParaPhraseAGH/skel_return_value

Skel return value
Merge pull request #8 from ParaPhraseAGH/random_insid_skel

Random inside skel
Code cleanup changes from Elvis.
Merge pull request #14 from ParaPhraseAGH/random_insid_skel

Code cleanup changes from Elvis.
Add aditional erlang releases.
Remove failing builds.

Erlang before 17 does not have `dict:dict` type, and will fail.
Add all models to simple tests runs.
Threat warnings as errors, and eliminate all warnings.

In addition updated `rebar` to new version.

This will fail if you do not update your deps
Shorter wait time for standard tests.
Baisic intergration test

This test fails, due to the way logging is implemented.
Ugly fix for testes, wait for global state to cleanup itself.
Make travis run only `ct` tests.