[IMP] store: connect function takes hash function in param

With this commit, we can now decides precisely if a component should be
rerendered, by using a hash function.

By default, the hash function will deep observe each store element
coming from the result of the mapStateToProps.

closes #24

examples/todoapp/templates.xml

@@ -50,7 +50,7 @@
             </label>
             <button class="destroy" t-on-click="removeTodo"></button>
         </div>
-        <input class="edit" t-ref="input" t-if="state.isEditing" t-att-value="props.title" t-on-keyup="handleKeyup" t-on-blur="handleBlur"/>
+        <input class="edit" t-ref="'input'" t-if="state.isEditing" t-att-value="props.title" t-on-keyup="handleKeyup" t-on-blur="handleBlur"/>
     </li>
 
 </templates>