Merge remote-tracking branch 'upstream/master' into rjl

* upstream/master:
  Remove plt usage that I accidentally added.
  Simple interactive plotting mode.
  Swallow IOErrors in Iplotclaw on 'n' or 'p' command.
  Don't swallow exceptions on file not found, unless in interactive mode.
  Fix frame detection in frametools to work with 4-digit frame numbers.
Merge branch 'rjl' into JSAnimation

* rjl: