Update sphinx docs; use exhale and breathe.

docs/sphinx/overview.rst

@@ -0,0 +1,26 @@
+.. _wrmath_api:
+
+Quick Overview
+==============
+
+Namespaces
+----------
+
+All WNTRMUTE code is in the ``wr`` namespace. The ``geom`` class is
+used for code concerning itself with realspace, e.g. :ref:`Quaternions
+<quaternion-docs>`.
+
+Coordinate systems
+------------------
+
+The library uses a left-hand coordinate system where +x is north, +y is
+east, and +z is up. Accordingly, where Euler angles are concerned, the
+ZYX (yaw / pitch / roll) axes are used.
+
+Important classes
+-----------------
+
+The foundational class of this library (and here's to a real mathematical
+workhorse) is the :class:`wr::geom::Vector`` class.
+
+Other important classes are the :class:`wr::geom::Quaternion` class.