Add command line option to render many documents

[f-f]

Fix #58

Adds a --manyDocs command line option to render a Dhall list as a list of YAML documents in the same stream. (suggestions welcome on a better name for the option)

I opened a patch to upstream (yaml) to have access to the YAML stream events (to add DocumentStart and DocumentEnd where needed), but just concatenating strings in this way is 10x less code and it's much easier to understand/maintain (IMO)

[jneira]

what about --split (or --list-split)? It is simpler and maybe more ambiguous, although i dont think in any overloaded meaning right now

[Gabriella439]

I would suggest --documents, mainly because (A) I try to avoid abbreviating words in user-facing options and (B) "many" is redundant since "docs"/"documents" is plural

[f-f]

Lovely, I'll go with --documents 👍

[Gabriella439]

@f-f: Looks great! Thanks for doing this 🙂