Remove before action from posts

Added allowed_to_modify_post? and post_owner?(post) to user model,
removed ensure_user_can_modify_post.

Fixed redirect bug in locations controller, now redirects to :locations

Changed link_to delete to button_to delete for UI consistency in
posts show.

Removed vertical spaces above "if" statements, unless it followed an
end.

Removed "self" from post_owner? conditional