Prevent staging loaderror with rescue in Rakefile

* Because guard-jasmine is in test/dev groups, guard rake task broke on staging
* Move guard rake task into begin rescue end block
* Source of Rakefile solution: https://devcenter.heroku.com/articles/ruby#rakefile
* Include test pattern in tddium.yml
Add jquery-migrate to the vendor folder

* In production only the Embed Feed was loading before the migrate script this is an attempt to fix that

https://trello.com/c/dfXzOuG7
Remove limit on invitation text

* Previous limit was 400 chars which was exceeded by a user
* Yammer API does not appear to enforce a limit

https://trello.com/c/vd8p6Vwc
wip