Add new style for numericalmooc notebooks

Work-in-progress, according to discussions
Style: background removed
Tweak the style

Style for h6 now used in copyright notice.
Tweak style, h2
Add sketch of forces on a glider
Add formulation of no-drag case, with sketch
Tweak style sheet
enable equation numbers in MathJAX using javascript hack in CSS
Add equation numbers, fig. captions & polish text

To add equation number must enclose in an equation or eqnarray
environment
Used color schemer for headings

http://www.colorschemer.com/online.html