Checkboxes in dropdown with geocoder

newbie here I'm using this dropdown which lists all countries with help of chosen-rails and country-select gem

<%= country_select :country, ['United States of America'], { include_blank: true }, { class: 'chosen-select' } %>

I want to do is have checkboxes in front of every country listed in dropdown with multiple selection and also I want to do something like this site is using

http://ift.tt/1mLvyEO

A search box in dropdown so that user can search through countries and also a functionality that after selecting his/her country he can search through area within 100miles or 50 miles .. . for this i come up with geocoder gem but unable to make it already wasted 2 days for this any kind of help would be appreciated.