New jsviewer css

In response to #2917, I have swapped in a lighter-weight CSS for the jsviewer table output. This also has some features like subtle row-highlighting (based on mouse-over) and column-highlighting (based on sort). Here's a short example (sorted on nobs and hovering over the 5th row).

![example-new-table](https://cloud.githubusercontent.com/assets/3639698/4412535/f4730b7c-44f9-11e4-86e2-76e9b3a35021.png)

The only problem is that I had to remove the in-line table styling https://github.com/jfoster17/astropy/commit/c1ea7b79fda2956d61019d42721b731185dcffd6
in order to make this table style look nice, which means that if the CSS doesn't load from the remote server, the fallback styling is normally pretty bad (this is browser/configuration dependent).  Perhaps someone else knows how to fix this?