Update TravisCI config

Add PHP 7.3, fix missing MySql service and fix allow_failures section

Author: JeroenDeDauw

.travis.yml

@@ -1,22 +1,24 @@
 language: php
 
+services:
+  - mysql
+
 matrix:
   fast_finish: true
   include:
-    - env: DB=mysql; MW=master; SMW=~3.0@dev
-      php: 7.1
+    - env: DB=sqlite; MW=master; SMW=~3.0@dev; TYPE=coverage
+      php: 7.3
     - env: DB=sqlite; MW=REL1_31; SMW=~3.0; MERMAID=dev-master
       php: 7.0
-    - env: DB=sqlite; MW=REL1_31; SMW=~3.0@dev; TYPE=coverage
+    - env: DB=mysql; MW=REL1_31; SMW=~3.0@dev
       php: 7.0
-    - env: DB=mysql; MW=REL1_32; SMW=~3.0@dev
+    - env: DB=postgres; MW=REL1_32; SMW=~3.0@dev
       php: 7.2
-    - env: DB=postgres; MW=REL1_33; SMW=~3.0@dev
+    - env: DB=mysql; MW=REL1_33; SMW=~3.0@dev
       php: 7.2
   allow_failures:
     # Broken due to https://phabricator.wikimedia.org/T188840
-    - env: DB=mysql; MW=master; SMW=~3.0@dev
-    - php: 7.2
+    - env: DB=mysql; MW=REL1_33; SMW=~3.0@dev
 
 install:
   - bash ./build/travis/install-mediawiki.sh