Added absent and present

Added and adapted the code for finding absent students provided on git hub
Added date select, absent students

Added a field to select what days attendance to view and the list of absent students
Added present and absent list though incomplete

Added the list of students In attendance above the full roster list.
At this time it is unclear as of to why not all students show as absent.

This was added in a rather crude manner unfortunately. I will trying to clean it
later on with making a _present.html.erb in my  attendances view and rendering it
though it was rather unsuccessful when I tried that with my exising index page. As
a result I moved the code.
Added absent handleing

Added the ability for the app to find who is not present  as well as setting
custom dates to view, if no date is selected it should defualt to todays.