Add require.js to static/components and load jQuery/require.js at the top of the page

This PR is to address this issue:

https://github.com/ipython/ipython/issues/5084

It adds a bower based require.js to `static/components` and puts both jQuery and require.js at the top of the body so they are available to subsequently loaded notebook cells.

@rgbkrk can we try this out on a test server first?

Also, I put these at the top of the body. Better to put them in the head?