Move the quick reference section to be first

The idea of making this section not be first is somewhat at odds with the
fact that it needs to link to the first page under Getting Started. It
would work to move it to the end, or to the beginning. The beginning
seems to be the "least surprise" choice for doc readers and contributors.

Author: sirosen

getting-started/index.rst

@@ -7,8 +7,8 @@ Getting started
 .. toctree::
    :maxdepth: 5
 
-   setup-building
    quick-reference
+   setup-building
    fixing-issues
    git-boot-camp
    pull-request-lifecycle