'search_contains' breaks search while escaping strings

[ninboy]

Chosen now escapes correctly the quotes in the values ('), but there is a problem with the escape string while the option "search_contains" is active.

If you have an item with a quote the search will try to match against ' and not ', making wrong results appear if you search for: #, x, 2, 7 or ;.

A small example is linked here: https://jsbin.com/luqusu/edit?html,output

Searching with search_contains = false makes the problem go away.

[IanSimpson]

This issue is also present if an optgroup or option contains any html special character - >, <, &, etc. I've submitted a PR with a proposed fix.