Add calendar presenter and utility classes

Add presenters for the new calendar and delete old helper file code.
Delete calendar erb and replace with slim file. Add active bool to
Schedule model for toggling schedules on/off easily and a scope
method for finding schedules that are active at any time in a date
range.
Remove students/calendar.html.erb view to replace with slim template
Modify presenters and start work on new calendar view

Update routes to point to new calendar view. Add application presenter
to hold generic code. Clean up SchedulePresenter to be a little
cleaner. Start new calendar css from scratch.
Clean up css, delete scaffold css, fix typography.

Changes made to clean up typography css and make the site more
consistent and readable.
Add overlaps? method to schedule model

Schedule#overlaps? checks to see if two schedules have overlapping
shifts. Will be used in the new calendar but is general enough to
go in the model.
Rename several asset files for clarity. Add calendar scss stylesheet.
Work on presentation code for calendar.
Progress on calendar rewrite.

Add ScheduleGroup class. JS is adjusting elements and resizing
schedules appropriately.
Finish ScheduleGroup initial code and update template code

ScheduleGroup and Schedulecalendar are updated. Template displays
initial changes without error. Still working on updating JS to
resize new ScheduleGroups. JSON will need to be updated as well and
then plenty of refactoring is in order.
Add color and nickname attributes to students. Improve validations
Continue updates to calendar

Further refactors of JS and calendar presentation code + classes.
Add schedulable.rb concern that helps composition of related
schedule presenters.
Layout redesign of students/show view

Convert students/show to slim. Add calendar display options form. Add
Support for nicknames and colors to student model. Add custom color
picker to form .
Complete color and nickname form. Clean up students controller.

Complete form view/frontend, controller actions, routes and model
changes for student display options.