Add HHVM and PHP7 to Travis

.travis.yml

 language: php
 
 php:
+  - 5.3
   - 5.4
   - 5.5
   - 5.6
+  - 7.0
+  - hhvm
+
+matrix:
+  fast_finish: true
+  allow_failures:
+    - php: hhvm
+    - php: 7.0
+
+sudo: false
 
 services: mongodb
 
@@ -11,11 +22,11 @@ before_script:
   - echo "extension = mongo.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini
   - mysql -e 'create database unittest;'
   - composer self-update
-  - composer install --dev --no-interaction
+  - travis_retry composer install --dev --no-interaction
 
 script:
   - mkdir -p build/logs
   - phpunit --coverage-clover build/logs/clover.xml
 
-after_script:
-  - php vendor/bin/coveralls -v
+after_success:
+  - sh -c 'if [ "$TRAVIS_PHP_VERSION" != "hhvm" ]; then php vendor/bin/coveralls -v; fi;'