Attempt to support newer google viewform urls

Based on https://github.com/jpf/TwilioSheet/issues/3#issuecomment-34660910
This should allow the newer google URLs to work.
Support newer html/simplify html scraping

Simplify the html scraping a bit
This appears to do the right thing:

https://docs.google.com/forms/d/1TLHCRZWsLt7huSzqlLoqA0MIHYT9n5xZRo4bRSotvlw/viewform
```python
>>> reload(gform)
<module 'gform' from 'gform.pyc'>
>>> s
'https://docs.google.com/forms/d/1TLHCRZWsLt7huSzqlLoqA0MIHYT9n5xZRo4bRSotvlw/viewform'
>>> k
'1TLHCRZWsLt7huSzqlLoqA0MIHYT9n5xZRo4bRSotvlw'
>>>
>>> G = gform.GForm(k, s)
>>> G.show_state( )
Parameters: {'entry.323738588': '', 'entry.1914238709': '', 'submit': 'Submit', 'entry.471541577': ''}
Labels: {'To': 'entry.1914238709', 'SmsSid': 'entry.323738588', 'From': 'entry.471541577'}
>>>

```

Without this patch I get the following errors:

```python
>>> reload(gform)
<module 'gform' from 'gform.py'>
>>> G = gform.GForm(k, s)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "gform.py", line 48, in __init__
    input_label = elements[0].text.rstrip()
AttributeError: 'NoneType' object has no attribute 'rstrip'
>>>

```