Update travis setup
Build with travis.cfg
Drop Plone 4.1 tests
exclude AT from default dependencies to not install ATContentTypes on Plone 5, tune travis and buildout.
Add an additional note for interface provider for dxcontent.
Only register archetypes adapter atct is installed.
Add missing plone-series in test-x.cfg
Use plone.app.robotframework
Merge remote-tracking branch 'origin/master' into copy-image-subscriber