Improve integration tests

[mburns]

What

Get integration tests working under CI.

TODO

• [x] run integration tests (in Docker) with Travis
• [x] use matrix features in TravisCI

Future Work

• [ ] support second platform (ubuntu 16, debian 8, etc)

[codecov-io]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@88b491f). Click here to learn what that means. The diff coverage is n/a.

@@           Coverage Diff           @@
##             master   #129   +/-   ##
=======================================
  Coverage          ?   100%           
=======================================
  Files             ?     15           
  Lines             ?    102           
  Branches          ?      0           
=======================================
  Hits              ?    102           
  Misses            ?      0           
  Partials          ?      0

Impacted Files	Coverage Δ
test/unit/spec/postfix_spec.rb	100% <ø> (ø)
test/unit/spec/spamassassin_spec.rb	100% <ø> (ø)
test/unit/spec/security_spec.rb	100% <ø> (ø)
test/unit/spec/system_spec.rb	100% <ø> (ø)
test/unit/spec/web_spec.rb	100% <ø> (ø)
test/unit/spec/multimedia_spec.rb	100% <ø> (ø)
test/unit/spec/email_spec.rb	100% <ø> (ø)
test/unit/spec/default_spec.rb	100% <ø> (ø)
test/unit/spec/roundcube_spec.rb	100% <ø> (ø)
test/unit/spec/wallabag_spec.rb	100% <ø> (ø)
... and 3 more

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Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 88b491f...1c9c479. Read the comment docs.

[mburns]

retest this please