Add command-line completion support for bash and zsh

[rahuliyer95]

• Fixes [Feature] autocomplete run #60
• Completions available for bash and zsh
• Don't know how to auto-install with pip. Any help here would be appreciated :)

[OrkoHunter]

Hi @rahuliyer95,

Thank you for taking on the feature request. I would also need your help to know how to use change. Could you also please make the following changes? Thanks!

• Add a section in the README (after Usage section) on how to use these completion scripts.
• Update Usage section with the new keep command.

[rahuliyer95]

I have updated the README to reflect the steps required to enable TAB completion on the command-line. I don't think the newly added completion command will ever be used by anyone as it outputs the stored commands specific to the shell of choice and has no direct use.

[OrkoHunter]

Thanks @rahuliyer95 ! Sounds good that it's fine not to document the command. I will get back on this.

[OrkoHunter]

Thanks @rahuliyer95 ! This looks good to me. Can you please resolve the README conflict and merge by yourself?

I moved README.rst to README.md and I'm unable to resolve conflicts in this PR. Sorry for the trouble. :)

[rahuliyer95]

Resolved the conflicts and can be merged