Specifying cython version to use

Change-Id: I6c0f03e582c33c57b5a6c7fe5f46429e010dd259
diff --git a/requirements.txt b/requirements.txt
index 6e785bd..389c862 100755
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,6 +1,6 @@
 argparse==1.2.1
 colorama>=0.2.5
-cython
+cython==0.24.1
 decorator>=3.4.0
 docker-py
 fluent-logger>=0.4.3