Bump version to v0.5.3

Signed-off-by: Jess Frazelle <acidburn@github.com>
diff --git a/VERSION.txt b/VERSION.txt
index b0c2058..4bc4a91 100644
--- a/VERSION.txt
+++ b/VERSION.txt
@@ -1 +1 @@
-v0.5.2
+v0.5.3