v1.6.1 - shell improvements

• #641 Improvements to shell

  Thanks django-extensions (licensed MIT) for the shell detection abstraction.

  • Deprecate shell_plus

  • tmuxp shell now detects the best shell available by default

  • Python 3.7+ with PYTHONBREAKPOINT set in env will drop into pdb by
    default

  • Drop into code.interact by default instead of pdb if no third
    party shells found

  • New options, override:

    • --pdb: Use plain old breakpoint() (python 3.7+) or
      pdb.set_trace
    • --code: Drop into code.interact, accepts --use-pythonrc
    • --bpython: Drop into bpython
    • --ipython: Drop into ipython
    • --ptpython: Drop into ptpython, accepts --use-vi-mode
    • --ptipython: Drop into ipython + ptpython, accepts
      --use-vi-mode