_Reader and _Writer have class filters for derived classes to use
modified tutorial.md [ci skip]
added update command to setup.py [ci skip]
refactored setup.py [ci skip]
_WriterBuffer.close() can safely be called more than once
ReaderSequence fix for empty input sequence
code and comment tweaks
revised tutorial.md [ci skip]
comment tweaks [ci skip]
added field.py module
converted reader.py module from using DataTypes to Fields
converted writer.py module from using DataTypes to Fields
removed dtype.py module
fix for _TabularReader when constructed with a fields generator
updated tutorial.md
improved tests for FixedWidthWriter
code clean-up
removed _StreamAdaptor.__enter__() and __exit__()
improved tests for FixedWidthReader
tweaked tutorial.md [ci skip]