Starting save button
Merge branch 'master' of https://github.com/Stanford-Online/class2go into jbau-save-button
Fixes #1543 -- Adds a "Save Answers" button + refactor + bugfixes

Bugfixes:
* Fixes #1764
* Fixes #1684

Refactors:
* get_or_create_incomplete_examrecord in exams/views.py
* Javascript function collectUserAnswers in view_exam.html
Button text save -> save answers
Add error message if save fails
removes print statments
Merge pull request #1766 from Stanford-Online/jbau-save-button

Jbau save button