Include license in pypi tarball (#92)

Needed for conda-forge packaging

MANIFEST.in

diff --git a/MANIFEST.in b/MANIFEST.in
index 54873cb..91e7ed3 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,4 +1,5 @@
 include *.rst
+include LICENSE.md
 recursive-include tools *
 recursive-exclude tools *.pyc
 recursive-include tests *