lintian: Add in explicit source format.

Change-Id: I05f7be162f38ccb2ecfd7f131d35f4f08ed4bfc8
diff --git a/debian/source/format b/debian/source/format
new file mode 100644
index 0000000..d3827e7
--- /dev/null
+++ b/debian/source/format
@@ -0,0 +1 @@
+1.0