Add hypothesis to Makefile

COUCHDB-2787
diff --git a/Makefile b/Makefile
index 8c136c1..1b2a504 100644
--- a/Makefile
+++ b/Makefile
@@ -46,6 +46,7 @@
 # target: pip-install - Installs requires Python packages
 pip-install:
 	pip install nose requests
+	pip install hypothesis
 
 
 .PHONY: venv