inboundxml: unicode string raises an Error in elements

[YAmikep]

A unicode string is not handled correctly in inboundxml Elements.
Please see below.
This appears with the Say element but the problem might be global and affect all the elements.

Thanks.

In [51]: str_string = 'test'
In [52]: unicode_string = u'test'

In [53]: print inboundxml.Say(str_string)
<Say>test</Say>

In [54]: print inboundxml.Say(unicode_string)
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-54-af1d388959b4> in <module>()
----> 1 print inboundxml.Say(unicode_string)

/python2.7/site-packages/telapi/inboundxml/__init__.pyc in __str__(self)
     29
     30     def __str__(self):
---> 31         return str(unicode(self))
     32
     33     def __unicode__(self):

/python2.7/site-packages/telapi/inboundxml/__init__.pyc in __unicode__(self)
     37         if not self._allow_blank and not body_string.strip():
     38             raise ValueError('The "%s" element cannot be blank!' %
---> 39                 self._element_name)
     40
     41         if len(self._attributes):

ValueError: The "Say" element cannot be blank!

[YAmikep]

I found where the problem was, here is the fix: #11
basestring should always be used to check whether a variable is a string to be compatible with both str and unicode strings.