Fix typo in tutorial.rst (#227)

docs/getting/tutorial.rst

@@ -4,7 +4,7 @@
 Tutorial
 **************************
 
-This example will show the simplist way to use pandas with pint and the underlying objects.
+This example will show the simplest way to use pandas with pint and the underlying objects.
 It's slightly fiddly to set up units compared to reading data and units from a file.
 A more typical use case is given in :doc:`Reading from csv <../user/reading>`.