Allow proxy settings to include protocol

http_proxy & https_proxy settings can now be specified with or without
the protocol prefix.

lib/geocoder/lookups/base.rb

@@ -99,7 +99,7 @@ module Geocoder
         protocol = "http#{'s' if configuration.use_https}"
         proxy_name = "#{protocol}_proxy"
         if proxy = configuration.send(proxy_name)
-          proxy_url = protocol + '://' + proxy
+          proxy_url = !!(proxy =~ /^#{protocol}/) ? proxy : protocol + '://' + proxy
           begin
             uri = URI.parse(proxy_url)
           rescue URI::InvalidURIError

test/proxy_test.rb

@@ -20,4 +20,16 @@ class ProxyTest < Test::Unit::TestCase
       Geocoder::Lookup::Google.new.send(:http_client)
     end
   end
+
+  def test_accepts_proxy_with_http_protocol
+    Geocoder.configure(:http_proxy => 'http://localhost')
+    lookup = Geocoder::Lookup::Google.new
+    assert lookup.send(:http_client).proxy_class?
+  end
+
+  def test_accepts_proxy_with_https_protocol
+    Geocoder.configure(:http_proxy => 'https://localhost')
+    lookup = Geocoder::Lookup::Google.new
+    assert lookup.send(:http_client).proxy_class?
+  end
 end