Drop mariadb: 5.5 tests

reorder matrix so all HHVM tests are at the bottom

.travis.yml

@@ -29,6 +29,25 @@ after_script:
 matrix:
   fast_finish: true
   include:
+    - php: 5.6
+      env: DB=mariadb
+      addons:
+        mariadb: 10.1
+    - php: 7.0
+      env: DB=mariadb
+      addons:
+        mariadb: 10.1
+    - php: 7.1
+      env: DB=mariadb
+      addons:
+        mariadb: 10.1
+    - php: hhvm
+      sudo: true
+      dist: trusty
+      group: edge # until the next Trusty update
+      addons:
+        mariadb: 10.1
+      env: DB=mariadb
     - php: hhvm
       sudo: true
       dist: trusty
@@ -55,45 +74,6 @@ matrix:
       group: edge # until the next update
       env: DB=sqlite
 
-    - php: 5.6
-      env: DB=mariadb
-      addons:
-        mariadb: 5.5
-    - php: 7.0
-      env: DB=mariadb
-      addons:
-        mariadb: 5.5
-    - php: 7.1
-      env: DB=mariadb
-      addons:
-        mariadb: 5.5
-    - php: hhvm
-      sudo: true
-      dist: trusty
-      group: edge # until the next Trusty update
-      addons:
-        mariadb: 5.5
-      env: DB=mariadb
-
-    - php: 5.6
-      env: DB=mariadb
-      addons:
-        mariadb: 10.1
-    - php: 7.0
-      env: DB=mariadb
-      addons:
-        mariadb: 10.1
-    - php: 7.1
-      env: DB=mariadb
-      addons:
-        mariadb: 10.1
-    - php: hhvm
-      sudo: true
-      dist: trusty
-      group: edge # until the next Trusty update
-      addons:
-        mariadb: 10.1
-      env: DB=mariadb
   allow_failures:
     - php: 7.1
     - php: nightly