requirements.txt: Tidy up file and add pylint version requirements

Turns out pylint upstream (1.3.0) has bugs that are triggered
by some of the autotest source files, whereas 1.2.0 works fine.

So, let's force pylint 1.2.0 for the time being.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
.travis.yml: Reorder setup steps

So that pylint 1.2.0 will be installed.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
requirements.txt: Force astroid version

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Merge pull request #865 from autotest/fix-travis

Fix travis