Prefer extension over shebang

lib/linguist/blob_helper.rb

@@ -80,7 +80,11 @@ module Linguist
 
     def language
       if text?
+        if pathname.extname == ""
           shebang_language || pathname.language
+        else
+          pathname.language
+        end
       else
         Language['Text']
       end

test/fixtures/blob/wrong_shebang.rb

@@ -0,0 +1,2 @@
+#!/usr/bin/env python
+puts "Not Python"

test/test_blob.rb

@@ -118,6 +118,7 @@ class TestBlob < Test::Unit::TestCase
     assert_equal Language['Ruby'], blob("foo.rb").language
     assert_equal Language['Ruby'], blob("script.rb").language
     assert_equal Language['Text'], blob("octocat.png").language
+    assert_equal Language['Ruby'], blob("wrong_shebang.rb").language
   end
 
   def test_lexer_name