Added vtr-xml-utils to requirements.txt

Signed-off-by: Maciej Kurc <mkurc@antmicro.com>
diff --git a/requirements.txt b/requirements.txt
index 0096dd6..31ca074 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,2 +1,3 @@
 lxml
 pyjson
+-e git://github.com/SymbiFlow/vtr-xml-utils#egg=vtr-xml-utils