Redirect user to the register page if not login in pp/views/register.erb

Added a #welcome-text id to public/css/create.css
JS updated to add slideDown on the register page public/js/style.js

Modified the Logo image in app/views/_nav.erb, splitted into 4 small images
-to add overlay with indication later- ,
CSS adapted for class nav in public/css/application.css

Title "Survey Jungle" added in app/views/layout.erb