Update README

README

-This is an example skeleton for developing out-of-tree Varnish vmods.
+This is an example skeleton for developing out-of-tree Varnish
+vmods. It implements the "Hello, World!" as a vmod callback. Not
+particular useful in good hello world tradition, but demonstrates how
+to get the glue around a vmod working.
+
+The source tree is based on autotools to configure the building, and
+does also have the necessary bits in place to do functional unit tests
+using the varnishtest tool.
 
 Usage:
 ./configure VARNISHSRC=DIR [VMODDIR=DIR]
@@ -11,4 +18,16 @@ Optionally you can also set the vmod install dir by adding VMODDIR=DIR
 (defaults to the pkg-config discovered directory from your Varnish
 installation).
 
+Make targets:
+make - builds the vmod
+make install - installs your vmod in VMODDIR
+make check - runs the unit tests in src/tests/*.vtc
+
+In your VCL you could then use this vmod along the following lines:
+
+import example;
 
+sub vcl_deliver {
+	# This sets resp.http.hello to "Hello, World"
+	set resp.http.hello = example.hello("World");
+}