Add extreme map example.

Author: clbanning

Diff for: anyxml.go

@@ -48,6 +48,9 @@
 		  <element>3.14159265</element>
 		  <element>true</element>
 		</mydoc>
+
+An example of encoding a map[interface{}]interface{} value with mixed key types is 
+in anyxml/examples/goofy_map.go.
 */
 package anyxml
 

Diff for: examples/goofy_map.go

@@ -0,0 +1,23 @@
+package main
+
+import (
+	"fmt"
+
+	any "github.com/clbanning/anyxml"
+)
+
+func main() {
+	data := map[interface{}]interface{}{
+		"hello": "out there",
+		1:       "number one",
+		3.12:    "pi",
+		"five":  5,
+	}
+
+	m, err := any.XmlIndent(data,"", "   ")
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	fmt.Println(string(m))
+}

Diff for: readme.md

@@ -60,3 +60,5 @@ output:
 	  <element>true</element>
 	</mydoc>
 </code></pre>
+
+An example of encoding a map with mixed key types is in anyxml/examples/goofy_map.go.