Remove PHP 5.3 from Travis build matrix and remove extra jobs to simplify

.travis.yml

@@ -4,18 +4,11 @@ language: php
 
 sudo: false
 
-php:
-  - 5.4
-  - 5.5
-
-env:
-  - DB=MYSQL CORE_RELEASE=3.5
-
 matrix:
   include:
-    - php: 5.3
+    - php: 5.4
       env: DB=PGSQL CORE_RELEASE=3.1
-    - php: 5.6
+    - php: 5.5
       env: DB=MYSQL CORE_RELEASE=3.2
     - php: 5.6
       env: DB=MYSQL CORE_RELEASE=3.3 SUBSITES=1
@@ -23,6 +16,8 @@ matrix:
       env: DB=MYSQL CORE_RELEASE=3.3 QUEUEDJOBS=1
     - php: 7.1
       env: DB=MYSQL CORE_RELEASE=3.6
+    - php: 7.1
+      env: DB=MYSQL CORE_RELEASE=3
 
 before_script:
   - composer self-update || true