modified TabularWriter comments
DelimitedReader::open() checks for fopen() failure
DelimitedWriter::open() checks for fopen() failure
FixedWidthReader::open() checks for fopen() failure
FixedWidthWriter::open() checks for fopen() failure
modified comments
refactored ArrayField.php
Field class renamed to ScalarField
fixed-width field values are fit to the allotted field width