add docs to sdist. fixes #679
diff --git a/MANIFEST.in b/MANIFEST.in
index 93d9551..8087077 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -4,6 +4,9 @@
 include LICENSE
 include README.rst
 
+recursive-include docs *
+prune docs/_build
+prune docs/_static
 recursive-include tests *.py
 recursive-include tests/vectors *
 recursive-include tests/hazmat/primitives/vectors *