Short term fix for preventing error when converting binary query params to json.

An error occurs when submitting a sqlalchemy query with binary data in the parameters.

In my specific example I was writing a new user with a hashed password that was binary.

This code demonstrates the underlying issue for me:

```python
import hashlib
import json
json.dumps({'password': hashlib.sha1('a').digest()})
```

```pythontraceback
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/json/__init__.py", line 231, in dumps
    return _default_encoder.encode(obj)
  File "/usr/lib/python2.7/json/encoder.py", line 201, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/lib/python2.7/json/encoder.py", line 264, in iterencode
    return _iterencode(o, 0)
UnicodeDecodeError: 'utf8' codec can't decode byte 0x86 in position 0: invalid start byte
```