Merge pull request #138 from settermjd/fix-typo-in-docs

Fix minor typo in contributing guide

Author: weierophinney

CONTRIBUTING.md

@@ -102,7 +102,7 @@ pull your work into the master repository. We recommend using
 3. Clone the canonical repository locally and enter it.
 
    ```console
-   $ git clone git://github.com:zendframework/zend-diactoros.git
+   $ git clone git://github.com/zendframework/zend-diactoros.git
    $ cd zend-diactoros
    ```