Simplify Dockerfile

Change-Id: I302dc1bf83115007919c9745912812fac8ac6648
diff --git a/requirements.txt b/requirements.txt
index 6e2edbd..cac5460 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,4 +1,4 @@
+joblib
 python-igraph
 setuptools
 tqdm
-joblib