add new random tip form
add category id and transavia to tip serializer
scope to search on category_id
refactor api/tips_controller to search for a user generated tip
add tips views and moving related views to follow convention
make transavia accessible to the tip
move new tip logic from city controller to tips index controller
leftover
rename tipscontroler to tipsindexcontroller
buttons send id instead of category slug
Merge branch 'refs/heads/develop' into feature/new_tip

Conflicts:
	app/assets/javascripts/templates/city.handlebars
	app/assets/javascripts/templates/tips/_tip.hbs
Merge pull request #2 from wirelab/feature/new_tip

new random tip to list