move demo documents into separate files

demo/docs/groovy.groovy

@@ -0,0 +1,26 @@
+//http://groovy.codehaus.org/Concurrency+with+Groovy
+import java.util.concurrent.atomic.AtomicInteger
+
+def counter = new AtomicInteger()
+
+synchronized out(message) {
+    println(message)
+}
+
+def th = Thread.start {
+    for( i in 1..8 ) {
+        sleep 30
+        out "thread loop $i"
+        counter.incrementAndGet()
+    }
+}
+
+for( j in 1..4 ) {
+    sleep 50
+    out "main loop $j"
+    counter.incrementAndGet()
+}
+
+th.join()
+
+assert counter.get() == 12