Add FID polyfill for Firebase Performance (gdg-x#611)

Add FID polyfill for Firebase Performance

Merge pull request gdg-x#538 from gdg-x/develop

v2.1.0

Replace a preview image

Fixed gdg-x#253 (gdg-x#254)

* Update dependencies

* Update dependencies

* Fix polymer-build

Update travis-ci config

Update My schedule icon on session element after sign out

Update Travis CI config

v1.0.4 (gdg-x#157)

* Fix filters label. Fix adblockers issue.

* fix route on speaker details (gdg-x#111)

* Fix speakers/schedule dialogs

* Hide language toggle if there is less than two languages available

* Fix gdg-x#114

* Add rel="noopener noreferrer" to all links with target="_blank". Fix gdg-x#113

* Center header image. Fix gdg-x#112

* fix errors in IE 11 (gdg-x#117)

* fix error in IE 11

* improve

* fix error in IE 11

* Add share buttons to post page. Fix gdg-x#97

* fix The Team page's layout is weird and team member photos don't seem to load (gdg-x#116)

* Add Tweetledee docs to the configuration part. Fixed gdg-x#49

* Update configure-app.md

* Add support of Polymer CLI v.0.16.0+

* Fix schedule filters in other than Chrome browsers. Fixed gdg-x#127

* Add webcomponents-lite library to a Polymer build process. Fix gdg-x#66

* Fix gdg-x#131

* Add fallback color for session/speakers dialog. Fix gdg-x#119

* Fix analytics error for featured videos. Minor fix in speaker/session dialog

* Fix function declaration in blog-list element. Fixed responsive issue on footer element

* add no-cache to mutable content

* get rif of redundant caching

* add no-cache to mutable content (gdg-x#136)

* add no-cache to mutable content

* get rif of redundant caching

* Get rid of docment.write (gdg-x#138)

* add no-cache to mutable content

* get rif of redundant caching

* get rif of document.write

* Fix social share image and corresponding meta data. Fixed gdg-x#141

* Fix header on mobile. Fixed gdg-x#142

* fix error in console

* Display speakers in one row when possible on session blocks

* Wrap legend on schedule legend

* fix error in console

* Remove language change noise in analytics

* Add presentations to sessions for showcase. Fix flattenBehaviors issue on a blog post

* Open schedule on the today's date. Fix gdg-x#153

* Make shorter short_name in manifest.json. Fix gdg-x#151

* Make toast full width on small screens

* Update margin on share button in session dialog

* Hide bottom block on sessions if there are no speakers

* Add share button to the footer. Fix gdg-x#156

v1.0.3 (gdg-x#139)

* Fix filters label. Fix adblockers issue.

* fix route on speaker details (gdg-x#111)

* Fix speakers/schedule dialogs

* Hide language toggle if there is less than two languages available

* Fix gdg-x#114

* Add rel="noopener noreferrer" to all links with target="_blank". Fix gdg-x#113

* Center header image. Fix gdg-x#112

* fix errors in IE 11 (gdg-x#117)

* fix error in IE 11

* improve

* fix error in IE 11

* Add share buttons to post page. Fix gdg-x#97

* fix The Team page's layout is weird and team member photos don't seem to load (gdg-x#116)

* Add Tweetledee docs to the configuration part. Fixed gdg-x#49

* Update configure-app.md

* Add support of Polymer CLI v.0.16.0+

* Fix schedule filters in other than Chrome browsers. Fixed gdg-x#127

* Add webcomponents-lite library to a Polymer build process. Fix gdg-x#66

* Fix gdg-x#131

* Add fallback color for session/speakers dialog. Fix gdg-x#119

* Fix analytics error for featured videos. Minor fix in speaker/session dialog

* Fix function declaration in blog-list element. Fixed responsive issue on footer element

* add no-cache to mutable content (gdg-x#136)

* add no-cache to mutable content

* get rif of redundant caching

* Get rid of docment.write (gdg-x#138)

* add no-cache to mutable content

* get rif of redundant caching

* get rif of document.write

Wrap secured token with double quotes