LatticeTiling: correct comments on Line 6 of nearest point algorithm

- Original rationale for change in rounding was wrong; real reason seems to
  be interaction with old initialization of 'y' from 'int_point' (removed in
  commit b157c70f0ec4f1b30296571a179737b9c6a4a7ee), and whether 'n + 1' is
  used outside the lround() or only inside it. No changes made to code.
Stop using deprecated keyword in numpy.histogram

new=True in numpy.histogram is discouraged since v1.3 and it's no
longer supported in recent versions, causing some scripts to fail
on Atlas. The default behavior now does the same thing.