Specifies precise for PHP 5.3, enables mongo extension

Author: prolificchrisb

.travis.yml

@@ -1,8 +1,15 @@
+matrix:
+  include:
+    - php: 5.3
+      dist: precise
+
 language: php
+
 php:
   - '5.3'
   - '5.4'
   - '5.5'
   - '5.6'
 
-install: travis_retry composer update --no-interaction --no-progress --no-suggest --prefer-stable
+before_install: echo "extension = <extension>.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini
+install: travis_retry composer update --no-interaction --no-progress --no-suggest --prefer-stable