Fix doc for `put_object` (#415)
Fix doc for `put_object` (#415)

Python's io.IOBase does not implement the read() method, but
io.RawIOBase does (in both major Python versions 2.7 and 3.5).
minio/minio-py,minio/minio-py,NitishT/minio-py,NitishT/minio-py,donatello/minio-py