HDFS, WebHDFS, HTTP I/O is not encoding-aware

[mpenkov]

The HDFS and Http subsystems does not do any text encoding or decoding.

• HdfsOpenRead returns the stdout from a Popen, so it will be in whatever encoding Popen uses for pipes (could be UTF-8, or raw bytes)
• HdfsOpenWrite writes bytes directly into the stdin of a Popen
• WebHdfsOpenRead reads bytes directly (requests.get returns bytes when stream=True)
• HttpOpenRead also reads bytes directly (uses requests in the same manner as above).

[mpenkov]

@menshikh-iv I think this is resolved by #185

[menshikh-iv]

@mpenkov 👍