Merge pull request php-http#181 from greg0ire/patch-1

Suggest latest version of the mock client

Author: dbu

httplug/library-developers.rst

@@ -53,7 +53,7 @@ in the ``require-dev`` section in your library’s ``composer.json``. You could
  "php-http/client-implementation": "^1.0"
  },
  "require-dev": {
- "php-http/mock-client": "^0.3"
+ "php-http/mock-client": "^1.0"
  }
  }