ensure utf-8 decode by default

[PopovK]

Hi,
it's a helpful tool you've done, but when trying to make it works under linux ubuntu, I ran into this critical error as soon as it reached a step requiring to decode the JSON data :

/dff/battle/get_battle_init_data called
Traceback (most recent call last):
File "FFRKProxy.py", line 113, in
...
File "FFRKProxy.py", line 70, in handle_response
json_data = json.loads(flow.response.content)
File "/usr/lib/python2.7/json/init.py", line 338, in loads
return _default_decoder.decode(s)
File "/usr/lib/python2.7/json/decoder.py", line 366, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/usr/lib/python2.7/json/decoder.py", line 384, in raw_decode
raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded

Problem is, it seems that by default on linux, it doesn't check or default to utf, the data type needs to be explicit.
I used the solution given here for Windows :
https://www.reddit.com/r/FFRecordKeeper/comments/34p36e/how_to_peek_items_drops_in_windows/cqwyroo

by adding a .decode('utf-8-sig') to all json.loads(flow.response.content), and it worked perfectly

Could you add this as default, or in a less static way, reuse in the json.loads the charset data from the http response-headers ?
It would fix both the issue on Windows and on some, if not all, linux distribs