v2.5.0: Multi-instance deployment and evaluation

== v2.5.0 Multi-instance deployment and evaluation

• Feature: npm run deploy-instances => batch deployment to several herokuapp.com apps
• Feature: redirectToHttps, publishSolutions and publishEvalTests config flags
• Feature: email-submit back-end (to hash answers for email delivery)
• Feature: display student name in header
• Feature: scores.csv splitted into one part per group
• Bug fix: auto-eval and realtime-eval now also works on Firefox and Safari
• Bug fix: Multi-variant exercises now also work using auto-eval in PUBLIC_TEST mode
• Bug fix: don't display score if null/undefined
• Bug fix: prevent crash with quizz questions that do not have a solution
• Refactoring: solutions and tests files are no longer necessary

Successfully tested for an exam of 75 students. (js-partiel-1)