Merge pull request #87 from proppy/fix-pdf

doc: switch to sphinxcontrib.rsvgconverter

docs/conf.py

diff --git a/docs/conf.py b/docs/conf.py
index 14d18bf..48571ef 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -59,7 +59,7 @@
     'sphinx.ext.mathjax',
     'sphinx.ext.napoleon',
     'sphinx.ext.todo',
-    'sphinx.ext.imgconverter',
+    'sphinxcontrib.rsvgconverter',
 ]
 
 # Add any paths that contain templates here, relative to this directory.