Expand edit functionality to support documents.

TODO:

- [x] wait for #45 
- [x] wait for #66.
- [x] create a generic file launching function that:
    - [x] wait for one second to let the process attempt to launch
    - [x] prompts 'Y/n' to import the modified files 
- [x] add document support to `doorstop edit ...`
- [x] refactor `_run*` functions into `commands.py`