BF: Update s3fs version.
BF: Update s3fs version.

I have been getting this error otherwise:

```
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-2-805623dd75d1> in <module>()
----> 1 from AFQ import api
      2 import AFQ.data as afd

3 frames
/usr/local/lib/python3.7/dist-packages/s3fs/core.py in <module>()
      9 from fsspec.spec import AbstractBufferedFile
     10 from fsspec.utils import infer_storage_options, tokenize
---> 11 from fsspec.asyn import AsyncFileSystem, sync, sync_wrapper, maybe_sync
     12
     13 import aiobotocore

ImportError: cannot import name 'maybe_sync' from 'fsspec.asyn' (/usr/local/lib/python3.7/dist-packages/fsspec/asyn.py)

```

arokem/pyAFQ,yeatmanlab/pyAFQ,arokem/pyAFQ,yeatmanlab/pyAFQ