1.8.3

• Improve S3 read performance by not copying buffer (PR #284, @aperiodic)
• accept bytearray and memoryview as input to write in s3 submodule (PR #293, @bmizhen-exos)
• Fix two S3 bugs (PR #307, @mpenkov)
• Minor fixes: bz2file dependency, paramiko warning handling (PR #309, @mpenkov)
• improve unit tests (PR #310, @mpenkov)