adding transition, error and complete states for assessment feedback form:

* provides static states for submission cases
* adds in abstracted system-feedback sass partial
* adds in starter animation sass partial
* syncs up loading style for steps with standards
* moves message UI archetypes/variables to the xblock level of Sass architecture

Move JS grade step into a separate file
Feedback on submission UI wiring
Generate JavaScript fixtures from Django templates
Adding start date validation to assessment modules
Merge pull request #215 from edx/sanchez/assessments_start_dates

Adding start date validation to assessment modules
Merge pull request #218 from edx/will/assessmentfeedback-submit

TIM-337: Feedback on assessment UI
Performance changes for staggered deadlines
This change improves the query when you have 35,000 open peer workflows and 0 assessments. Performance appears to still be good for a fluid workflow as well.
Merge pull request #221 from edx/sanchez/more_performance_improvements

Performance changes for staggered deadlines
adding transition state for form inputs' placeholder UI
making step__status elements' visual width equal in all cases
cleaning up step__title and step__status UI for responsive layouts
adding visual emphasis to problem's prompt UI
adding graded + required UI back into step__status for peer assessment templates
adding collapse/expand toggle to assessment feedback form UI
aligning step__status icons/text to be left-justified
revising introductory message copy
adding visual spacing between grade report UI sections
finalizing assessment feedback UI
syncing up step__status positioning for larger desktops