FIX: Modernise travis build matrix

- SS 3.6 works with PHP 7.1
 - PHP 5.3 testing is no longer feasible
 - Deprecated use of precise no longer needed

.travis.yml

@@ -4,22 +4,15 @@ sudo: false
 
 language: php
 
-dist: precise
-
 php:
-  - 5.3
   - 5.4
   - 5.5
   - 5.6
-  - 7.0
+  - 7.1
 
 env:
   - DB=MYSQL CORE_RELEASE=3
 
-matrix:
-  allow_failures:
-    - php: 7.0
-
 before_script:
   - composer self-update || true
   - git clone git://github.com/silverstripe-labs/silverstripe-travis-support.git ~/travis-support