Fix issue #40: bug in blank query detection.

Was ignoring non-ASCII characters. Thanks to github.com/supergivi for
reporting the bug.

lib/geocoder.rb

@@ -131,7 +131,7 @@ module Geocoder
   # Is the given search query blank? (ie, should we not bother searching?)
   #
   def blank_query?(value)
-    !value.to_s.match(/[A-z0-9]/)
+    !!value.to_s.match(/^\s*$/)
   end
 end
 

test/geocoder_test.rb

+# encoding: utf-8
 require 'test_helper'
 
 class GeocoderTest < Test::Unit::TestCase
@@ -213,8 +214,9 @@ class GeocoderTest < Test::Unit::TestCase
   def test_blank_query_detection
     assert Geocoder.send(:blank_query?, nil)
     assert Geocoder.send(:blank_query?, "")
-    assert Geocoder.send(:blank_query?, ", , (-)")
+    assert Geocoder.send(:blank_query?, "\t  ")
     assert !Geocoder.send(:blank_query?, "a")
+    assert !Geocoder.send(:blank_query?, "Москва") # no ASCII characters
   end
 
   def test_does_not_choke_on_nil_address