Motion view dev

This branch contains some major changes in the `pydy.viz` module. Which I am listing here. I am opening this Pull request to have a final review before it is merged.  @moorepants @chrisdembia @jcrist @srjoglekar246

P.S: I am working on JS-Testing in a separate branch #74  I plan to get this one merged once that is complete, and merged into `motion-view-dev`.

 - A new, better UI.
 - Integration with IPython notebooks. For rendering the visualizer inside the IPython notebooks, simply call `scene.display_ipython` from a notebook. (Works only on latest master of IPython).
 - Now rendered objects can be modified from the UI itself(using `edit objects` button in UI), and new JSON will be generated, which can be viewed by clicking `view model` button in UI.
 - Added a new property "material" to the rendered shapes (`Shape` object).
 - Allows rerunning the simulations(after changing the simulation parameters) from the visualizer itself. This feature is partially implemented, but will be fully functional once `System` class comes in.
 - Javascript backend completely modified. Now it is object oriented using Prototype.js.


**Instructions for building this branch with latest IPython, and testing the new features:**

1. Cloning and installing latest IPython:

    $ git clone https://github.com/ipython/ipython ipython-dev
    $ cd ipython-dev
    $ git submodule update
    $ pip install -e .

2. get this branch from git repo:

    $ git checkout --track origin/motion-view-dev

3. Add it to PYTHONPATH. 

    $ export $PYTHONPATH="/your/pydy/repo/:$PYTHONPATH"

4. Now you can check out the `double_pendulum` example. 
    - cd to examples/double_pendulum
    - comment out the last line in visualize.py, this one: https://github.com/pydy/pydy/blob/motion-view-dev/examples/double_pendulum/visualize.py#L64
    - open `$ ipython notebook`
    - from the notebook call:

    from visualize import *
    scene.display_ipython()

Please feel free to contact me, if there are any difficulties!!