added different lang links to head for google

services/web/app/coffee/infrastructure/ExpressLocals.coffee

@@ -51,6 +51,7 @@ module.exports = (app)->
 
 	app.use (req, res, next)->
 		res.locals.translate = req.i18n.translate
+		res.locals.currentUrl = req.originalUrl
 		next()
 
 	app.use (req, res, next)->

services/web/app/views/layout.jade

@@ -13,6 +13,10 @@ html(itemscope, itemtype='http://schema.org/Product')
 		link(rel='stylesheet', href='/stylesheets/style.css?fingerprint='+fingerprint('/stylesheets/style.css'))
 		link(href="//netdna.bootstrapcdn.com/font-awesome/4.1.0/css/font-awesome.min.css",rel="stylesheet")
 
+
+		each subdomainDetails in settings.i18n.subdomainLang
+			link(rel="alternate", href=subdomainDetails.url+currentUrl, hreflang=subdomainDetails.lngCode)
+
 		meta(itemprop="name" ,content="ShareLaTeX - Real Time Online LaTeX Collaborative Editor in Your Browser")
 		meta(itemprop="description", content="Online LaTeX editor for collaborative editing, great for Maths or Sciences. You don't need to install LaTeX so it's great for beginners too.")
 		meta(itemprop="image", content="https://www.sharelatex.com/favicon.ico")