Merge pull request #141 from tkowark/develop

Fixed chair show and refactored chairs controller
Merge remote-tracking branch 'origin/develop' into realmaster
Merge remote-tracking branch 'origin/develop' into develop-ak
added initial chair_pages_spec and made chair controller + user model a little more robust against permission violation
more chair tests
added some users controller tests
Merge branch 'develop-ja' of https://github.com/tkowark/hpi-hiwi-portal into develop-ja
Merge branch 'develop-ja-matching-job-offers' of https://github.com/tkowark/hpi-hiwi-portal into develop-ja-matching-job-offers
changed the algorithm for selecting matching job offers for a student and renamed the button in the student show view