Fix N5 link in tutorial (#480)

Author: jrbourbeau

docs/tutorial.rst

@@ -746,7 +746,7 @@ with `MongoDB <https://www.mongodb.com/>`_ (an oject oriented NoSQL database). T
 respectively require the `redis <https://redis-py.readthedocs.io>`_ and
 `pymongo <https://api.mongodb.com/python/current/>`_ packages to be installed. 
 
-For compatibility with the `N5<https://github.com/saalfeldlab/n5`_ data format, Zarr also provides
+For compatibility with the `N5 <https://github.com/saalfeldlab/n5>`_ data format, Zarr also provides
 an N5 backend (this is currently an experimental feature). Similar to the zip storage class, an
 :class:`zarr.n5.N5Store` can be instantiated directly::