Add stub for executor

Still not sure what/how this will look

src/exec.rs

@@ -0,0 +1,13 @@
+/**
+ * This is the simple executor module.
+ */
+
+use log::*;
+
+pub struct Executor {
+}
+
+impl Executor {
+    fn run() {
+    }
+}

src/main.rs

@@ -7,6 +7,7 @@ extern crate serde_json;
 use log::*;
 
 mod dao;
+mod exec;
 mod routes;
 mod state;