Added parsing of artboard layer data

lib/psd/layer/info.coffee

@@ -15,6 +15,7 @@ Util = require '../util.coffee'
 # node.get('typeTool').export()
 # ```
 LAYER_INFO = {
+  artboard:               require('../layer_info/artboard.coffee')
   blendClippingElements:  require('../layer_info/blend_clipping_elements.coffee')
   blendInteriorElements:  require('../layer_info/blend_interior_elements.coffee')
   fillOpacity:            require('../layer_info/fill_opacity.coffee')

lib/psd/layer_info/artboard.coffee

+LayerInfo = require '../layer_info.coffee'
+Descriptor = require '../descriptor.coffee'
+
+module.exports = class Artboard extends LayerInfo
+  @shouldParse: (key) -> key is 'artb'
+
+  parse: ->
+    @file.seek 4, true
+    @data = new Descriptor(@file).parse()
+
+  export: ->
+    coords:
+      left: @data.artboardRect['Left']
+      top: @data.artboardRect['Top ']
+      right: @data.artboardRect['Rght']
+      bottom: @data.artboardRect['Btom']