added past proc to appointment model
added two new instance variables, past appts for mentors and mentees, to users controller
added helper method to determine the tense phrase
edited the appointment partial to take into account the tense
added HTML for past appointments to user edit page
added helper method spec for tense
limited number of displayed past appointments to 5
changed helper method name tense to future_or_past_tense
added feature tests for mentor and mentee to see past appointments
Merge pull request #107 from copperheads-2014/view-past-appointments

View past appointments