Update travis to remove PHP versions < 5.4 and add PHP7

.travis.yml

@@ -1,12 +1,10 @@
 language: php
 
 php:
-  - 5.2
-  - 5.3
-  - 5.3.3
   - 5.4
   - 5.5
   - 5.6
+  - 7.0
   - hhvm
  
 matrix:
@@ -18,7 +16,6 @@ before_script:
   - sudo apt-get -qq update > /dev/null
   ## Composer
   ##@todo Remove when support of 5.2 will be dropped
-  - phpenv global 5.3
   - composer self-update
   - composer install --prefer-source --dev
   - phpenv global "$TRAVIS_PHP_VERSION"