Bump the php-code-coverage requirement

php-code-coverage:2.0.11 was the first version to require phpunit/php-token-stream:~1.3
which had a fix for the @runInSeparateProcess on hhvm

Author: duncan3dc

composer.json

@@ -24,7 +24,7 @@
         "php": ">=5.3.3",
         "phpunit/php-file-iterator": "~1.3.2",
         "phpunit/php-text-template": "~1.2",
-        "phpunit/php-code-coverage": "~2.0",
+        "phpunit/php-code-coverage": "~2.0,>=2.0.11",
         "phpunit/php-timer": "~1.0.2",
         "phpunit/phpunit-mock-objects": "~2.3",
         "phpspec/prophecy": "~1.3.1",