V0.2.1

Fixed some strange errors on brython to make brythonmagic works fine on the Jupyter notebook.

• Added some functions to easily load javascript libraries that can be used by brython in the notebook:
  • load_brython_stable: will load the latest brython_dist.js stable release from http://www.brython.info/src/brython_dist.js.
  • load_brython_dev: will load the latest brython_dist.js development version from github using rawgit.
  • load_js_lib: Allows you to load javascript libs using a string indicating the url.
• Updated the code to make it work with latest jupyter releases.