DOC: stop using deprecated sphinx extensions

Author: tacaswell

doc/source/conf.py

@@ -36,7 +36,6 @@
     'sphinx.ext.mathjax',
     'sphinx.ext.viewcode',
     'sphinx.ext.autosummary',
-    'matplotlib.sphinxext.only_directives',
     'matplotlib.sphinxext.plot_directive',
     'IPython.sphinxext.ipython_directive',
     'IPython.sphinxext.ipython_console_highlighting',

doc/source/index.rst

@@ -4,7 +4,7 @@
  Composable cycles
 ===================
 
-.. htmlonly::
+.. only:: html
 
     :Version: |version|
     :Date: |today|