Created student model tests. Coverage on student model is 100 per cent.

Files Modified.

modified:   Gemfile
modified:   Gemfile.lock
modified:   app/views/layouts/application.html.haml
modified:   app/views/students/new.html.haml
deleted:    spec/helpers/feed_helper_spec.rb
deleted:    spec/helpers/home_helper_spec.rb
deleted:    spec/helpers/sessions_helper_spec.rb
deleted:    spec/helpers/students_helper_spec.rb
modified:   spec/models/student_spec.rb
modified:   spec/spec_helper.rb