remove pecl imagick install from hhvm builds

Author: mike42

.travis.yml

@@ -29,7 +29,7 @@ install:
 
 before_script:
   # Install 'imagick' plugin
-  - printf "\n" | pecl install imagick
+  - bash -c 'if [[ $TRAVIS_PHP_VERSION != hhvm* ]]; then printf "\n" | pecl install imagick; fi'
   # Directory for coverage report
   - mkdir -p build/logs/