Use Travis CI Container-based infrastructure and added PHP nightly an…

…d HHVM testing

.travis.yml

@@ -1,14 +1,24 @@
 language: php
 
-php:
-  - 5.4
-  - 5.5
-  - 5.6
-
-before_script:
-  - composer self-update
-  - composer install
-  - mkdir -p build/logs
+sudo: false
+
+matrix:
+  include:
+    - php: 5.4
+    - php: 5.5
+    - php: 5.6
+    - php: nightly
+    - php: hhvm
+  allow_failures:
+    - php: nightly
+    - php: hhvm
+  fast_finish: true
+
+before_install: composer self-update
+
+install: composer install
+
+before_script: mkdir -p build/logs
 
 script: vendor/bin/phpunit --coverage-clover build/logs/clover.xml