added trackback url for photo page
open trackback url in new tab
paged flickr result
Merge branch 'feature/flickr' into develop

Conflicts:
	Gemfile
	app/views/pois/_form.html.erb
	db/schema.rb
UI tweak
protect pages from non-users
fixed bug at selecting flickr image in new POI
added validations to user, poi, trip
sort POI based on popularity
clear votes and set not confirmed when a trip is deleted
Merge branch 'release/2.0'