Fix preview window (Closes #1)

lineage/lib/__init__.py
- Add new class `TempLineage`: for storing temporary lineages (without
  using a basic list)
- Add new function `get_offset`: for calculating crop bounds, outline
  shifts, and offsets
- Make grand-mother cells yellow rather than blue to avoid confusion
- Fix preview issues: add grand-parent frame, add death frame (if not
  death due to lack of frames), fix issues with moving out of image
  boundaries
- Make matplotlib figure window full-screen by default