BUG,DOC,ENH,UBY: don't strip empty lines

[westurner]

"empty" lines are currently stripped out

• An 'empty' line is "" or really \n or \r\n or \r,
  as iterated by e.g. file.__iter__.

## The outputs here are all equivalent:
# (echo -e "here\n\n"; ls -a) | pyline
# (echo -e "here\n\n"; ls -a) | pyline 'l'
$ (echo -e "here\n\n"; ls -a) | pyline 'l and l'
here


.
..

These all output no lines and return 0; because
pyline does strip out values that eval to False with Python bool()
after an expression; e.g.:

$ (echo -e "here\n\n"; ls -a) | pyline 'l and ""'
$ (echo -e "here\n\n"; ls -a) | pyline 'l and False'
$ (echo -e "here\n\n"; ls -a) | pyline 'l and None'

TODO

Is this a bug?

It could be configurable. e.g. --print-null, -no-strip-empty

Options:

• [-], --strip-empty-lines, --strip-empty
• [-], --no-strip-empty-lines, --no-strip-empty

[westurner]

see also: #18