coala-travis.yml.jj2: Create custom template

The new template extends from pypi-mobans template, importing default blocks from coala/coala repository, and customised to work on coala-quickstart.

Includes pre-installation of lxml, to match the solution in .ci/deps.python-packages.ps1, until a better solutionis created.

Related to https://github.com/coala/coala-bears/issues/2940

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Implemented at https://github.com/coala/coala/pull/6054 and https://github.com/coala/coala-quickstart/pull/338