Changes in version 0.3 -----------------------------------------------------------------

* Import stringr instead of depending on it

* Test plot recording only in the presence of interactive devices.

Changes in version 0.2 -----------------------------------------------------------------

* try_capture_stack and create_traceback do a much better job of removing
  infrastructure calls from the captured traceback

* visible results are automatically evaluated and their outputs are captured.
  This is particularly important for lattice and ggplot graphics, which
  otherwise require special handling. It also correctly captures warnings,
  errors and messages raised by the print method.