Fixed recognition of "forty"

I spelled it "fourty", which tricks the lmtool into making it much
harder to recognize the word.  Now it's spelled "forty", which makes it
much easier to understand.

kayleevc/numbers.py

     tens = {
         'twenty': 20,
         'thirty': 30,
-        'fourty': 40,
+        'forty': 40,
         'fifty': 50,
         'sixty': 60,
         'seventy': 70,