Add progress bars to index page
Fix failing test for index page progress bar
Add tooltips to issue progress bars on index page
Fix failing test because of previous commit
Small design change for progress bar tooltips on index page
Make data_attributes method private in TagHelper
Show long text to solvers just once

Solver will see long explanation text just once. Once he sign up for
some issue, he will not see long text when signing up to another issue.
Add category page which list all issues in given category
Add index page for all issues
Add rack-mini-profiler to development environment
Replace Issue#smt_count with Issue#smts_count (db column)
Add link to all issues below random issues on index page
Add SMT stats
Fix failing test because of previous factory change
Add Admin Solvers stats
Add possibility to choose if Issue is published or not

* add default scope to Issue to find just published issues
* modify tests and factories
Add possibility to delete issues