Added simple user guide in README.

README.rst

@@ -1,5 +1,5 @@
-Generic -- programming library for Python
-=========================================
+Generic programming library for Python
+======================================
 
 Generic is trying to be simple and easy-to-use programming library that
 features the following:
@@ -10,3 +10,29 @@ features the following:
 * Event system (not implemented).
 
 Its development takes place at http://githib.com/andreypopp.
+
+Multidispatching
+----------------
+
+Generic library provides way to define function with multidispatching feature::
+
+    from generic.multidispatching import multifunction
+
+    @multifunction(int, int)
+    def add(x, y):
+        return x + y
+
+    @add.when(str, str)
+    def add(x, y):
+        return add(int(x), int(y))
+
+And then in console::
+
+    >>> add(1, 2)
+    3
+    >>> add("1", "2")
+    3
+    >>> add("1", 2)
+    Traceback
+    ...
+    TypeError: ...