fix for DatetimeField.encode() and fixed-width null values
simplified MANIFEST.in and fixed portability issues [ci skip]
added ReaderSequence class
added deprecation warning for ReaderSequence
refactored DelimitedReader to fix Python 3 deprecation warnings
refactored DelimitedWriter to fix Python 3 deprecation warnings
test code clean-up
modified SequenceReader calling convention
comment typo fixes and tweaks [ci skip]
refactored SequenceReader and improved tests
refactored BufferedIStream
SequenceReader.close() can safely be called more than once
comment tweaks [ci skip]
removed SequenceReader.close()
added AggregateReader class
added AggregateWriter class
renamed AggregateReader/Writer.apply() method to reduce()
added tests for aggregate.py module
added reduction() function
changed reduction semantics in AggregateReader/Writer