Emit an event when a page is added

Use the document as the EventEmitter

Update docs

docs/getting_started.coffee.md

@@ -85,6 +85,11 @@ quite simple!
     
     doc.addPage()
 
+To add some content every time a page is created, either by calling `addPage()` or automatically, you can use the `pageAdded` event.
+    
+    doc.on 'pageAdded', ->
+      doc.text "Page Title"
+
 You can also set some options for the page, such as it's size and orientation.
 
 The `layout` property can be either `portrait` (the default) or `landscape`.

lib/document.coffee

@@ -99,6 +99,8 @@ class PDFDocument extends stream.Readable
     # the top left rather than the bottom left
     @_ctm = [1, 0, 0, 1, 0, 0]
     @transform 1, 0, 0, -1, 0, @page.height
+
+    @emit('pageAdded')
     
     return this