Update .travis.yml

Updating to take advantage of Travis-CI containers.

.travis.yml

@@ -1,5 +1,7 @@
 language: php
 
+sudo: false
+
 php:
   - 5.3.3
   - 5.3
@@ -8,9 +10,8 @@ php:
   - 5.6
 
 before_script:
-  - composer self-update
-  - composer update --prefer-source
-  - composer install --no-interaction --dev --prefer-source
+  - composer self-update 1.0.0-alpha10
+  - composer install --no-interaction --prefer-source
 
 script:
   - ./vendor/bin/phpunit