refactors thumbnail url getter
adds a fallback icon for the back arrow button
with bugfixes:
Merge branch 'master' of heroku.com:iupb-beta into develop
# By Dirk Schumacher
# Via Dirk Schumacher
* 'master' of heroku.com:iupb-beta:
  update method also updates the youtube urls (further room for improvements ;))
fixes and closes #27
adds a responsive recaptcha
fixes and closes #24
Merge branch 'develop' of https://github.com/dirkschumacher/iUPB into develop
removes unused gem sanitize
forgot to commit updated gemfile.lock
amends last commit
Merge branch 'develop' of https://github.com/dirkschumacher/iUPB into develop
corrects a typo
first try infinite loading with jquery.pageless. (#34)
but only loads second page...
minor refactoring in ads coffee script
disables the query pageless plugin -> normal pagination
Merge branch 'develop' of https://github.com/dirkschumacher/iUPB into develop

# By Dirk Schumacher
# Via Dirk Schumacher
* 'develop' of https://github.com/dirkschumacher/iUPB:
  minor refactoring in ads coffee script
disables ads in production mode
Merge pull request #28 from dirkschumacher/develop

iUPB Version V2 with pinboard feature develop -> master