Travis : allow failure for php 7.0/7.1 and add php 7.3
Travis : allow failure for php 7.0/7.1 and add php 7.3

Signed-off-by: Guillaume Roques <e72d67a579ee335440d38eb209db13892007b977@gmail.com>

MediaArea/MediaArea-Website,MediaArea/MediaArea-Website,MediaArea/MediaArea-Website