put lambda function back in, as requested during code review

Small cleanups in response to Calen + Piotr's comments

Courseware can have same random seed in multiple problems for exam. 

Add video volume control to video player

Victor/render path cleanup

* Refactor index() so that it makes sense to me and hopefully others :)
* Rename preloaded cache of student modules to student_module_cache
* Fix line length and whitespace throughout
* add docstrings and other comments
* a few behavior-preserving tweaks to the code to make it clearer.
* Separate codepaths for with-module and without-module in index view
* Remove default chapter + section, since they don't exist anyway in course.xml

Create Calculator and Feedback form on every page

Using `.ui-slider-handle` was too broad.

Victor/create docs

Coding standards document

Added django_nose and nosexcover to requirements.txt

Capa cleanup