add simple tcp test

dev/tests/network.lua

@@ -0,0 +1,19 @@
+local data = "hello, world"
+local complete = false
+
+network.tcp_open(7645, function (client)
+    start_coroutine(function()
+        local received = client:recv(1024)
+        if received then
+            assert (data, utf8.tostring(received))
+            complete = true
+        end
+        coroutine.yield()
+    end, "client-listener")
+end)
+
+network.tcp_connect("localhost", 7645, function (socket)
+    socket:send(data)
+end)
+
+app.sleep_until(function () return complete end)