More work on lesson components

J and A,

I spent the morning and early afternoon today working on the lesson detail page. Quite a few commits. The gist is:

* Added markup for all of the lesson contents based on this lesson: http://www.engageny.org/sites/default/files/resource/attachments/3m2a.2l2_1.pdf
* Added styles for the lesson components and expanded/revised base styles to handle content-heavy tables and nested ordered and unordered lists
* Refined styling for jump links, buttons and tag list at top of detail page