lintian: Add in an explicit source format

Change-Id: Idc890eaa12a746f4b00944b0efe556dd6e9941a5
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