Initial port of ipywidget support

Added js/ directory containing front-end widget library
Added graph_objs.FigureWidget class that maps to datatypes.FigureWidget

Author: Jon M. Mease

Diff for: .gitignore

@@ -27,3 +27,8 @@ plotly/datatypes
 plotly/validators
 
 .idea
+
+js/node_modules/
+
+# Compiled javascript
+plotlywidget/static/

Diff for: contributing.md

@@ -112,6 +112,11 @@ To install the optional dependencies:
 pip install -r optional-requirements.txt
 ```
 
+## ipywidget development install
+    $ jupyter nbextension enable --py widgetsnbextension
+    $ jupyter nbextension install --py --symlink --sys-prefix plotlywidget
+    $ jupyter nbextension enable --py --sys-prefix plotlywidget
+
 ## Testing
 
 We take advantage of two tools to run tests:

Diff for: js/README.md

@@ -0,0 +1,11 @@
+pythonic plotly API for use in Jupyter
+
+Package Install
+---------------
+
+**Prerequisites**
+- [node](http://nodejs.org/)
+
+```bash
+npm install --save plotlywidget
+```