Add php 7/hhvm, add non-interactive to install, test lowest

Author: barryvdh

.travis.yml

@@ -1,18 +1,29 @@
 language: php
 
-os:
-  - linux
-  - windows
-
 php:
   - 5.3
   - 5.4
   - 5.5
   - 5.6
+  - 7.0
+  - hhvm
+
+env:
+  global:
+    - setup=basic
 
-before_script:
+matrix:
+  include:
+    - php: 5.3
+      env: setup=lowest
+    - php: 5.3
+      env: setup=stable
+      
+install:
   - composer self-update
-  - composer install
+  - if [[ $setup = 'basic' ]]; then composer install --no-interaction; fi
+  - if [[ $setup = 'stable' ]]; then composer update --no-interaction --prefer-stable; fi
+  - if [[ $setup = 'lowest' ]]; then composer update --no-interaction --prefer-lowest --prefer-stable; fi
   - phpenv rehash
 
 script: