Slightly expand issue/lag docs
Slightly expand issue/lag docs

The R and Python client documentation contains extended examples that
will be useful for novice users; we can treat the API docs here as being
for advanced users.

cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata,cmu-delphi/delphi-epidata