Support to diacritics match during filtering

[mvrioe]

This version allows matching characters with accents/diacritics during filtering
e.g. "évidemment" is matched with "evidemment".
Using algorithm suggested in http://stackoverflow.com/questions/990904/remove-accents-diacritics-in-a-string-in-javascript by rdllopes

Algorithm hardcoded to avoid packages dependencies

This is achieved by setting the enableDiacriticsMatchFiltering option as true.

[davidstutz]

Definitely a good feature. However, impossible to merge due to the formatting changes. Will try to merge it manually.

[chukhanhvan]

I see a lot of PR in recent days, do you plan to add this diacritics feature? I like bootstrap-multiselect but diacritics is the only reason to still use select2