added ratings.json
deleted talk.html; a talk's details are displayed in details.html, so talk.html can be deleted.
nex version of rating. the API has changed, now the server should calculate the average rating and also determine whether the user has already rated a presentation or not.
added first test for RatingService
added reminding comment
added '/' + USER_TOKEN to the commented code to clarify my intention
Merge pull request #72 from SchweizerischeBundesbahnen/feature/mfr/delete-talk-html

deleted talk.html
Merge pull request #73 from SchweizerischeBundesbahnen/feature/mfr/rating

Feature/mfr/rating
Merge branch 'develop' into feature/mfr/hyphenation