chore(prepare 4.51): Update core to 7.73...
chore(prepare 4.51): Update core to 7.73 https://www.drupal.org/sa-core-2020-007. Update modules wetkit_core and wetkit_bootstrap. Add php7.3 to travis ci.
chore(prepare 4.51): Update core to 7.73 https://www.drupal.org/sa-core-2020-007. Update modules wetkit_core and wetkit_bootstrap. Add php7.3 to travis ci.