Update travis configuration
Update travis configuration

Follow OCA/maintainer-quality-tools#187 and use addons/apt/package directive to
install our build dependencies. This allows using container based Travis builds
(which should be faster).

syci/website-odoo,Yajo/website,xpansa/website,RoelAdriaans-B-informed/website,Antiun/website,Benniphx/website,incaser/website,Antiun/website,Rona111/website,StefanRijnhart/website,AuyaJackie/website,sergio-incaser/website,open-synergy/website,gfcapalbo/website,Rona111/website,seb-elico/website,BT-fgarbely/website,LasLabs/website,sergio-incaser/website,pedrobaeza/website,xpansa/website,gfcapalbo/website,initOS/website,pedrobaeza/website,Tecnativa/website,Tecnativa/website,gfcapalbo/website,nuobit/website,Endika/website,StefanRijnhart/website,sergio-incaser/website,nuobit/website,nuobit/website,RoelAdriaans-B-informed/website,nuobit/website,hbrunn/website,hbrunn/website,acsone/website,open-synergy/website,brain-tec/website,BT-fgarbely/website,seb-elico/website,Yajo/website,JayVora-SerpentCS/website,kaerdsar/website,pedrobaeza/website,khaeusler/website,BT-jmichaud/website,RoelAdriaans-B-informed/website,AuyaJackie/website,Antiun/website,LasLabs/website,acsone/website,BT-fgarbely/website,AuyaJackie/website,Yajo/website,incaser/website,Endika/website,Rona111/website,xpansa/website,incaser/website,Benniphx/website,acsone/website,pedrobaeza/website,khaeusler/website,kaerdsar/website,nicolas-petit/website,Tecnativa/website,initOS/website,RoelAdriaans-B-informed/website,BT-ojossen/website,brain-tec/website,hbrunn/website,open-synergy/website,seb-elico/website,BT-ojossen/website,nicolas-petit/website,xpansa/website,syci/website-odoo,Yajo/website,open-synergy/website,nicolas-petit/website,BT-jmichaud/website,khaeusler/website,LasLabs/website,Antiun/website,syci/website-odoo,gfcapalbo/website,initOS/website,BT-jmichaud/website,BT-ojossen/website,StefanRijnhart/website,kaerdsar/website,Endika/website,acsone/website,brain-tec/website,LasLabs/website,Endika/website,Benniphx/website,brain-tec/website,JayVora-SerpentCS/website,JayVora-SerpentCS/website