Backwards compatibility for python < 3

Python 2.6 doesn't support keyword arguments for str.encode.  Positional arguments work for both Python 2 and 3.

Python 2.6.6 Example of error stacktrace 
```
  File "/usr/lib/python2.6/site-packages/pyes/es.py", line 1059, in count
    path = self._make_path(indices, doc_types, "_count")
  File "/usr/lib/python2.6/site-packages/pyes/es.py", line 434, in _make_path
    return make_path(','.join(indices), ','.join(doc_types), *components)
  File "/usr/lib/python2.6/site-packages/pyes/utils/__init__.py", line 37, in make_path
    path_components = [quote(component) for component in path_components if component]
  File "/usr/lib/python2.6/site-packages/pyes/utils/__init__.py", line 17, in quote
    value = value.encode('utf8', errors='ignore') if isinstance(value,  six.string_types) else str(value)
TypeError: encode() takes no keyword arguments
```