add dependency.
new reader/writer implementation started.
HeaderCSVReader calls CSV.new.
renamed.
rename get_header to get_named_header.
refine the file explanation.
remove tempfile at finish.
numeric csv implemented.
HeaderTSVReader and HeaderTSVWriter implemented.
files renamed.
Change header mixins to classes
Change hash reader/writer mixins to classes.
Change numeric reader/writer mixins to classes.
JSONReader2 and JSONWriter implemented.
LTSVReader2 and LTSVWriter implemented.
Fix a variable reference.
include Tb::Enumerable.
Refine unexpected field handling.
Add put_finish argument.
PNMReader2 defined.