Convert strings to Decimal values

Punt string handling to python Decimal object, this correctly represents both
integers and floats (except with regards to trailing zeros)
Change command line tests to reflect handling of ints

num2words/__init__.py

@@ -96,6 +96,8 @@ def num2words(number, ordinal=False, lang='en', to='cardinal', **kwargs):
     if lang not in CONVERTER_CLASSES:
         raise NotImplementedError()
     converter = CONVERTER_CLASSES[lang]
+    if isinstance(number, str):
+        number = converter.str_to_number(number)
     # backwards compatible
     if ordinal:
         return converter.to_ordinal(number)

num2words/base.py

@@ -96,6 +96,9 @@ class Num2Word_Base(object):
             return '%s ' % self.negword, num_str[1:]
         return '', num_str
 
+    def str_to_number(self, value):
+        return Decimal(value)
+
     def to_cardinal(self, value):
         try:
             assert int(value) == value