added routes and controller for tip creation
tip categories can now be selected
added username and user avatar to tip form
fix hover, data attribute was renamed earlier
tip title can now be entered
link, address and description can now be filled in
add validations to tip
added todo for headline and removed it from params
display the correct variables of a tip
show the author avatar in the tip
added couple todos
tip image can now be uploaded (ugly way)
image is now uploadable via the "foto toevoegen" link
only try to set a current_user if the session is present
display the error if category isn't valid
show image preview
added a (not yet working) link validator and changed the show to thank you
removes link validation
Merge branch 'refs/heads/develop' into feature/tip_creation

Conflicts:
	app/models/tip.rb
	db/schema.rb
fixed the responsiveness of the create tip page