No longer rely on the DOM to deselect last selection

When choosing an option in a single select, we need to update the
array of options to deselect any previously selected options.
result_single_selected is no longer used
Move some repeated logic into abstract chosen
Make sure selected items are cleared after resetting Chosen single
Remove superfluous variable update
Update our policy on bug reporting

fixed typo

Another typo
Merge pull request #1470 from harvesthq/closing_issue_policy

Update our policy on bug reporting
Merge pull request #1461 from harvesthq/g1458-fix-single-selected-result

Single select results in sync
Docs should state that we (maintainers) will reopen issues.
Merge pull request #1501 from harvesthq/reopen_issue_policy

Docs should state that we (maintainers) will reopen issues.