Simplify example instructions and fix broken examples

Also convert to AsciiDoc while we're at it.

examples/echo_get/README.asciidoc

@@ -0,0 +1,28 @@
+= GET parameter echo example
+
+To try this example, you need GNU `make` and `git` in your PATH.
+
+To build and run the example, use the following command:
+
+[source,bash]
+$ make run
+
+Then point your browser to http://localhost:8080/?echo=hello
+
+You can replace the `echo` parameter with another to check
+that the handler is echoing it back properly.
+
+== Example output
+
+[source,bash]
+----
+$ curl -i "http://localhost:8080/?echo=saymyname"
+HTTP/1.1 200 OK
+connection: keep-alive
+server: Cowboy
+date: Fri, 28 Sep 2012 04:09:04 GMT
+content-length: 9
+content-type: text/plain; charset=utf-8
+
+saymyname
+----