New DFFD update method throws errors when failing

[Pidgeot]

ERROR: Error downloading http://dffd.bay12games.com/file_data/.json: Not Found
ERROR: Error checking for updates
Exception in thread Thread-1:
Traceback (most recent call last):
  File "C:\Python34\lib\threading.py", line 920, in _bootstrap_inner
    self.run()
  File "C:\Python34\lib\threading.py", line 868, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Users\~\Documents\GitHub\python-lnp\core\update.py", line 39, in perform_update_check
    if lnp.updater.update_needed():
  File "C:\Users\~\Documents\GitHub\python-lnp\core\update.py", line 143, in update_needed
    self.get_version() != lnp.config.get_string('updates/packVersion'))
  File "C:\Users\~\Documents\GitHub\python-lnp\core\update.py", line 247, in get_version
    self.json = JSONConfiguration.from_text(self.text)
  File "C:\Users\~\Documents\GitHub\python-lnp\core\json_config.py", line 46, in from_text
    return JSONConfiguration(None, json.loads(text))
  File "C:\Python34\lib\json\__init__.py", line 312, in loads
    s.__class__.__name__))
TypeError: the JSON object must be str, not 'NoneType'

This is probably because I'm getting the configuration wrong, but there shouldn't be an exception there. As well as checking the None issue, could you provide example valid configs for the Update object in the readme? Mine is below, and I've tried the number as a string and an int without any difference.

  "updates": {
    "updateMethod": "dffd",
    "dffdId": "7622"
  }

[Issue created by PeridexisErrant: 2015-05-03]

[Comment created by Pidgeot: 2015-05-03]
Add error message during updating if pack version is not set (fixes #88)
Add update configuration examples to readme

→ <<cset 8b3d54ff8193>>

[Comment created by Pidgeot: 2015-05-03]
You need to set packVersion - that's what's failing.

I'll add an error message when that one is missing.