Travis update (rebased onto metadata53)

[jburel]

This is the same as gh-5409 but rebased onto metadata53.

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What this PR does

Use trusty to build
This is necessary to build with newer version of pytables
and newer version of ice

• building using ant fails all the time, need to use ./build.py.
• installation of python dependencies needs to be explicitly done via
  sudo apt-get during before_install: otherwise the dependencies will not be available to the container. This means that the python tests will fail with for example No module Ice. Change sudo option to required. I did not notice an increase in the build time with that change. See Issue with the Python path in the recent builds travis-ci/travis-ci#8048
• update numexpr via pip to avoid some table test failure e.g.
  test/unit/tablestest/test_servants.py:349: will fail with ValueError: Using `oa_ndim == 0` when `op_axes` is NULL. Use `oa_ndim == -1` or the MultiNew iterator for NumPy <1.8 compatibility

Testing this PR

Check that travis is green

See https://trello.com/c/gVsUkLH8/100-travis-upgrade

[jburel]

--rebased-from #5409

[jburel]

Closing something did not work when using scc