Merge pull request #35 from djheels/patch-2

Typo in Tutorial 2

docs/tutorial/tutorial-2.rst

@@ -152,7 +152,7 @@ We're still creating a main box; however, we are now applying a style::
             main_box = toga.Box(style=Pack(direction=COLUMN))
 
 Toga's builtin layout system is called "Pack". It behaves a lot like CSS. You
-define objects in a heirarchy - in HTML, the objects are ``<div>``, ``<span>``,
+define objects in a hierarchy - in HTML, the objects are ``<div>``, ``<span>``,
 and other DOM elements; in Toga, they're widgets and boxes. You can then assign
 styles to the individual elements. In this case, we're indicating that this is
 a ``COLUMN`` box - that is, it is a box that will consume all the available