Fix/extract long seq toscripts

[themangoemoji]

No description provided.

[themangoemoji]

test this please

[mr-c]

since -l is required it shouldn't be in brackets. The easiest thing to do is to copy the relevant lines from running your script with --help here.

[mr-c]

• Is it mergable
• Did it pass the tests?
• If it introduces new functionality in scripts/ is it tested?
  Check for code coverage.
• Is it well formatted? Look at pep8/pylint, cppcheck, and
  make doc output. Use autopep8 and astyle -A10 --max-code-length=80
  if needed.
• Is it documented in the Changelog?
• Was spellcheck run on the source code and documentation after changes
  were made?

[mr-c]

• ChangeLog and I'll merge this.

[mr-c]

Thanks!

[ctb]

Well, but wait. Do we have any other scripts that require a command line option? This is un-UNIX-like (as the term "option" suggests, command-line options should be optional). I would prefer either a default value of 200 (+1) or a required positional argument (as before) over a command-line option (-0 in general, -1 here since AFAIK no other scripts in khmer follow this strategy).

This needs to be addressed before 1.0.2 release, n.b.