Git ignore mango .hypothesis directory

This ignores a directory created by a dependency of the mango test suite.
diff --git a/.gitignore b/.gitignore
index 99a5285..eaa50a6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -121,6 +121,7 @@
 src/mango/test/*.pyc
 src/mango/nosetests.xml
 src/mango/venv/
+src/mango/.hypothesis/
 src/jwtf/.rebar3/
 test/javascript/junit.xml