Added foreign key constraint between exzweight and machine.  Set up relation
between exzweight where 1 exzweight has 1 machine.

Also, changed exzweight forms to display machine as company / model /
exercise_type.

 On branch master
 Your branch is up-to-date with 'origin/master'.

 Changes to be committed:
	modified:   Gemfile
	modified:   Gemfile.lock
	modified:   app/controllers/exzweights_controller.rb
	modified:   app/controllers/machines_controller.rb
	modified:   app/models/exzbike.rb
	modified:   app/models/exzweight.rb
	modified:   app/models/machine.rb
	modified:   app/views/exzweights/_form.html.erb
	modified:   app/views/exzweights/index.html.erb
	modified:   app/views/exzweights/show.html.erb
	modified:   config/routes.rb
	deleted:    db/migrate/20140610200408_adapt_exzweights_to_machines.rb
	new file:   db/migrate/20140611132115_fit_exzweight_to_machine.rb
	new file:   db/migrate/20140611133314_remove_model_from_exzweight.rb
	new file:   db/migrate/20140617175556_add_foreign_key_to_exzweight.rb
	new file:   db/migrate/20140617195058_change_date_default.rb
	modified:   db/schema.rb