Multiple changes in CDN links

Multiple changes in CDN links

* Moving the resources from CDNJs to JSDelivr. In HTTP/2 and SPDY it is recommended to host all dependencies in the same CDN or web server, so all resources are downloaded using the same HTTP connection. It's faster than establish a connection to two CDN providers. In the past using multiple CDN was the best option, but no longer. So we have to put them in just one CDN, I don't have any relation with JSDelivr but think is the best available option.
* Added SRI (integrity) to external scripts. This prevents an infection if the CDN is compromised.
* Removed version aliasing from Algolia (3) and put specific version (3.13.1). This way the cache TTL is longer and avoid breaking changes if the library is updated.
* Added the JSDelivr RUM script. This allow them to test the performance of downloading scripts and takes better load balancing decision for the CDN resources.