Add json support

The munchkin xAPP needs lightweight json, as might other xAPPs,
so it makes sense to do the work onece and add it to the framework.

Issue-ID: RIC-420

Signed-off-by: E. Scott Daniels <daniels@research.att.com>
Change-Id: I20ea999ba77566d1404f0d69be0f63669943236e
diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..a88d7ab
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "ext/jsmn"]
+	path = ext/jsmn
+	url = https://github.com/zserge/jsmn