Freeze package on analysis compatibility

[sarahmish]

Current tests are failing due to travis setting on Xential, for py36 it fails due to numpy version difference within packages in mlprimitives. Problem is we need mlprimitives on version 0.1.6 for the analysis.

To fix this, I changed travis dist to bionic.

[sarahmish]

py35 also fails on travis due to timeout

$ tox
GLOB sdist-make: /home/travis/build/DAI-Lab/Cardea/setup.py
py35 create: /home/travis/build/DAI-Lab/Cardea/.tox/py35
py35 inst: /home/travis/build/DAI-Lab/Cardea/.tox/.tmp/package/1/cardea-0.0.2.zip

No output has been received in the last 10m0s, this potentially indicates a stalled build or something wrong with the build itself.
Check the details on how to adjust your build configuration on: https://docs.travis-ci.com/user/common-build-problems/#build-times-out-because-no-output-was-received
The build has been terminated

EDIT
proposed fix to use travis_wait.