Update PHP version syntax

We should be more specific with the PHP version. We are not testing for PHP8 and PHP9 but our composer file said that we support it. =)

Author: Nyholm

composer.json

@@ -12,7 +12,7 @@
  }
  ],
  "require": {
- "php": ">=5.4.0",
+ "php": "^5.4|^7.0",
  "egeloen/http-adapter": "~0.8|~1.0",
  "igorw/get-in": "~1.0"
  },