Add bash auto completion support

[cdrage]

Adds auto completion support that's generated via:

$ kompose complete

This file is added to /etc/bash_completion.d/kompose.sh

[cdrage]

Closes #37

[coveralls]

Coverage remained the same at 47.007% when pulling 15a1946 on cdrage:add-autocompletion into 2ba8831 on kubernetes-incubator:master.

[ngtuna]

Kompose should create the file if it's not exist.

./kompose completion
Error: open /etc/bash_completion.d/kompose.sh: no such file or directory

[cdrage]

@ngtuna It should. Doesn't look like you're running as sudo / have user permission to /etc/bash_completion.d/

Try sudo ./kompose completion

[ngtuna]

Ah see it now... It doesn't work on Mac. Could we add this support to darwin ?

[surajssd]

works on fedora for me 👍

[kadel]

Can we do it like kubectl or oc? Print to stdout instead to file? (https://kubernetes.io/docs/user-guide/kubectl/kubectl_completion/) or at least have option for it.

I don't think that it is no nice write to /etc by default without any warning.

I really like that stdout option, because if you put source <(kubectl completion bash) to you bashrc,
completion is always up to date, you don't have to remember regenerate it with new kubectl version

[kadel]

And one more. Some people are using ZSH (like me for example 😉 )

[cdrage]

@kadel Alright :) I'll do these three things:

1. Output to stdout
2. Add the ZSH option (btw @kadel zsh > bash. #zshmasterrace)
3. Add support for Darwin

[cdrage]

@ngtuna @kadel

Ready for another review!

It now does:

1. Outputs to stdout 👍
2. Added bash support 👍
3. For the users who use a laptop with a magical touchbar that removes the ESC key, you can simple source it with source <(kompose completion bash). 👍

[kadel]

👍
Tested ZSH and Bash on Linux, and just ZSH on MacOS

[cdrage]

@kadel

Tests should be all green now (validate error with some unreachable code).

I've also updated the README with the appropriate instructions on how to use this!

Merge when you're ready 👍

[kadel]

LGTM @ngtuna can you confirm?

[ngtuna]

Yes. Confirmed