Added some usage info to the Readme

README.markdown

@@ -1,3 +1,35 @@
 # Peity
 
 Peity (sounds like deity) is a simple jQuery plugin to create a mini pie chart from the contents of an element using canvas.
+
+## Usage
+
+
+### HTML
+
+    <span class="chart_1">2/10</span> 
+    <span class="chart_2">4/10</span> 
+    <span class="chart_3">5/10</span> 
+
+### Javascript (jquery)
+
+    $(function(){
+      $('span').peity();
+    });
+
+## Updating charts
+
+Peity adds a "change" event trigger to your graph elements, so if you update their data your can regenerate one or more charts by triggering "change" on them.
+
+   $('span#chart_1').html("5/10").trigger('change')
+
+## Subscribing to chart updates
+
+After drawing the chart, Peity elements will trigger the event 'peity:changed', passing current and maximum values as event arguments. This is useful if you want to "listen" to chart updates elsewhere in your code:
+
+   $('span').bind('peity:changed', function(event, new_value, max_value){
+     $('p#notice').html("Chart updated: " + new_value + " out of " + max_value);
+   });
+
+See a working example in examples/simple.html
+