Revised documentation in preparation for v0.3

The "tutorial" has been split out into a number of separate chapters.
This should significantly enhance readability and findability.

.gitmodules

@@ -1,3 +0,0 @@
-[submodule "doc/sphinxext/numpydoc"]
-	path = doc/sphinxext/numpydoc
-	url = https://github.com/numpy/numpydoc.git

doc/_static/dataset-diagram.tex

@@ -257,13 +257,13 @@
         emphstyle=very thick,
     }
     \node [font=\fontsize{11}{11}\selectfont] at (18,11.5) {temperature};
-    \node [font=\fontsize{11}{11}\selectfont] at (23,11.5) {pressure};
+    \node [font=\fontsize{11}{11}\selectfont] at (23,11.5) {precipitation};
     \node [font=\fontsize{11}{11}\selectfont] at (25.8,11.5) {latitude};
     \node [font=\fontsize{11}{11}\selectfont] at (27.5,11.47) {longitude};
     \node [font=\fontsize{11}{11}\selectfont] at (28,10) {x};
     \node [font=\fontsize{11}{11}\selectfont] at (29.5,8.5) {y};
-    \node [font=\fontsize{11}{11}\selectfont] at (32,7) {z};
-    \node [font=\fontsize{11}{11}\selectfont] at (31,10) {time};
+    \node [font=\fontsize{11}{11}\selectfont] at (32,7) {t};
+    \node [font=\fontsize{11}{11}\selectfont] at (31,10) {reference\_time};
     \fill (31,9.5) circle[radius=2pt];
 \end{tikzpicture}
 

doc/api-hidden.rst

@@ -0,0 +1,60 @@
+.. Generate API reference pages, but don't display these in tables.
+.. This extra page is a work around for sphinx not having any support for
+.. hiding an autosummary table.
+
+.. currentmodule:: xray
+
+.. autosummary::
+   :toctree: generated/
+
+   Dataset.all
+   Dataset.any
+   Dataset.argmax
+   Dataset.argmin
+   Dataset.max
+   Dataset.min
+   Dataset.mean
+   Dataset.prod
+   Dataset.sum
+   Dataset.std
+   Dataset.var
+
+   Dataset.isnull
+   Dataset.notnull
+
+   Dataset.argsort
+   Dataset.clip
+   Dataset.conj
+   Dataset.conjugate
+   Dataset.round
+   Dataset.T
+
+   DataArray.ndim
+   DataArray.shape
+   DataArray.size
+   DataArray.dtype
+   DataArray.astype
+   DataArray.item
+
+   DataArray.all
+   DataArray.any
+   DataArray.argmax
+   DataArray.argmin
+   DataArray.max
+   DataArray.min
+   DataArray.mean
+   DataArray.prod
+   DataArray.sum
+   DataArray.std
+   DataArray.var
+
+   DataArray.isnull
+   DataArray.notnull
+
+   DataArray.argsort
+   DataArray.clip
+   DataArray.conj
+   DataArray.conjugate
+   DataArray.searchsorted
+   DataArray.round
+   DataArray.T