Updated model and controller to allow voting

* New column 'votes' on Idea model
* RESTful routes for IdeasController
* member action 'upvote' for IdeasController
* specs

USe XHR to update the votes

Finish xhr; use image

Feature specs
Merge remote-tracking branch 'swalberg/6_vote'

Conflicts:
	app/controllers/ideas_controller.rb
	app/views/ideas/index.html.slim
	config/routes.rb
	spec/controllers/ideas_controller_spec.rb