Simplified slides.js

Just removed some unneeded code and replaced jQuery with alias object $.

Simplified function calls, which reduces amount of transfered sourcecode to the client.
Simplified list_user.rb

This should do the same but without fetching the arel table.
Simplified list_user.rb

Removed unneeded if code.
Removed outdated code

Well, I think that there won't be any support for Rails 2 or later, doesn't it? As Redmine itself is shifting to Rails 4 and personally the latest supported Versions of Redmine just run with Rails 3.2.x, this won't be needed, what do you think?
Merge branch 'master' of https://github.com/CodeInsider/redmine_workload
Merge branch 'patch-1' of https://github.com/CodeInsider/redmine_workload
Merge branch 'patch-2' of https://github.com/CodeInsider/redmine_workload
Merge branch 'patch-3' of https://github.com/CodeInsider/redmine_workload