A workaround for the impossibility to install different requirements-files for different Python versions at travis-ci.org.
Now able to install the dependencies from everywhere.
Making the tests run under Python 3.
With unicode literals in place the workaround is not limited to Python 3.
Merge branch 'master' of https://github.com/ralsina/nikola
Merge pull request #221 from okin/master

Fix issue #215 & wordpress import test