Auto-generation bash script to perform completions for a given CLI

[jdegoes]

Bash is a common shell for Linux / BSD operating systems. Bash has a feature whereby you can have the shell auto-complete options for a command-line argument, which can simplify usage of command-line applications.

See here for a tutorial and here for more extensive documentation.

Given a CLI, we should be able to nicely generate a bash script that when sourced, will add all appropriate completions using the complete process.

See CLIApp#completions.

[jdegoes]

More details here: #3

[ashprakasan]

I'll take a stab at this.

[harveywi]

I'd like to give this a go 😎 If anyone else is interested, feel free to join me.

[harveywi]

Whew! #107

[harveywi]

Here's a PR that implements the rest of the tab completion machinery for Bash: #119