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).

luca-vercelli/l10n-italy,odoo-isa/l10n-italy,linkitspa/l10n-italy,linkitspa/l10n-italy,alessandrocamilli/l10n-italy,hurrinico/l10n-italy,maxhome1/l10n-italy,linkitspa/l10n-italy,abstract-open-solutions/l10n-italy,scigghia/l10n-italy