No more check_executable, check extname instead.

When File.executable?() is used, it checks if the file is an
executable AND that exe permission is set. Well, we don't really
have to set the permission we can still load/use the module. So
really, all we care is the module must be a ".rb" to make sure
it loads at startup.  So that's what we need to check.

tools/msftidy.rb

@@ -58,9 +58,9 @@ class Msftidy
 	#
 	##
 
-	def check_executable
-		if not File.executable?(@name)
-			warn("File is not executable. Double check your file type and permissions.")
+	def check_extname
+		if File.extname(@name) != '.rb'
+			error("Module should be a '.rb' file, or it won't load.")
 		end
 	end
 
@@ -228,7 +228,7 @@ end
 
 def run_checks(f_rel)
 	tidy = Msftidy.new(f_rel)
-	tidy.check_executable
+	tidy.check_extname
 	tidy.test_old_rubies(f_rel)
 	tidy.check_ranking
 	tidy.check_disclosure_date