Add support to get certificate chain as separate certificates

[mikemunger]

https://github.com/afosto/yaac/issues/10

Hello there, I have added the enhancement we discussed in issues.

Let me know if you'd like any adjustments before you'd accept it.

Thanks!

[bakkerpeter]

Thanks for the PR, will look into this tomorrow!

[bakkerpeter]

Thanks @mikemunger! Edit: whoops, wrong button :)

[bakkerpeter]

Allright, that's it :)