I think its just a namespace issue. You need to remove include GeoKit::Geocoders
. I looked in geocoder source and can't find anything GeoKit
$ pwd
/usr/local/rvm/gems/ruby-2.0.0-p247/gems/geocoder-1.1.8/lib
$ find . | xargs grep -i GeoKit
$
So I googled and apparently there's another gem called geokit. The namespace you've mentioned gets resolved in this gem at line 92. And this GeoCoder class obviously doesn't have a search method. So I suspect you've a reference to geokit in your Gemfile.
And btw I use just geocoder & it works fine on my environment -
$ rails console
Loading development environment (Rails 4.0.0)
2.0.0-p247 :001 > zip_code = '94301'
=> "94301"
2.0.0-p247 :002 > aaa = Geocoder.search(zip_code).first.coordinates
=> [37.4457966, -122.1575745]
2.0.0-p247 :003 >