Remove PHP 5.3 from Travis config, shuffle tested SS versions

.travis.yml

@@ -4,22 +4,16 @@ sudo: false
 
 language: php
 
-php:
-  - 5.3
-  - 5.4
-  - 5.5
-
-env:
-  - DB=MYSQL CORE_RELEASE=3.5
-
 matrix:
   include:
+    - php: 5.4
+      env: DB=MYSQL CORE_RELEASE=3.3
+    - php: 5.5
+      env: DB=MYSQL CORE_RELEASE=3.4
     - php: 5.6
+      env: DB=PGSQL CORE_RELEASE=3.5
+    - php: 7.0
       env: DB=MYSQL CORE_RELEASE=3
-    - php: 5.6
-      env: DB=MYSQL CORE_RELEASE=3.1
-    - php: 5.6
-      env: DB=PGSQL CORE_RELEASE=3.2
     - php: 7.1
       env: DB=MYSQL CORE_RELEASE=3.6