Indexedredis

- Add support for BINARY_FIELDS -- directly storing data as binary.
This is a better option in most cases than BASE64_FIELDS, takes much
less time, and is more space efficient
- Implicitly make the FIELDS defined on models to be sets in __init__

- Fix py3 install

- Add "connect" method to IndexedRedisModel, which allows using models
with an alternate redis instance than that on the parent model. It returns
a "class" that inherits the IndexedRedisModel with the
REDIS_CONNECTION_PARAMS updated to reflect those as passed in.

- Remove accidental addition of not-finished code

- Updates to documentation and examples

- Change very basic existing model validation to a one-time call, and
validate on more things.
- *EXCITING* - Implement BASE64_FIELDS on IndexedRedisModel. Any
FIELDS that also show up in BASE64_FIELDS will be base64-encoded
before storage and decoded upon retrieval. This makes it possible and
very simple to use "bytes" or other binary data. You may need this,
for example, to store files or other blobs.