Remove unused index route for images
Refactor redundant use of gallery_path(@gallery)
Refactor redundant path syntax
Refactor image partial for clarity
Refactor images_controller

* Add find_gallery and find_image_in(gallery) private methods
* Update all actions to use these methods
* Break image_params method into multiple lines for clarity
A few minor view updates

* Add Home link in layouts/application.html.erb
* Remove welcome message when signed in; just show email
* Use <nav> tags instead of <div> tags where appropriate
* Move link to gallery above image in images/show.html.erb