Feature/34 copy notes from one date to another

[ioanniswd]

Adds a command to copy notes from one date to another:

Examples

Copy notes from yesterday to today, in the default category

$ stup copy

Copy notes from a specific date, to a specific date

$ stup copy --from 2020-01-15 --to 2020-02-01

Copy notes from yesterday to tomorrow in the category "blocking"

$ stup copy --to tomorrow -c blocking

Resolves #34

[ioanniswd]

Sorry for the force pushes, had to change author in commits. No changes in code.

[iridakos]

@all-contributors please add @ioanniswd for code :rocket:

[allcontributors[bot]]

@iridakos

I've put up a pull request to add @ioanniswd! :tada: