Support "link objects"

[danpoland]

From http://jsonapi.org/format/#document-links:

Each member of a links object is a “link”. A link MUST be represented as either:

• a containing the link’s URL.
• an object (“link object”) which can contain the following members:
  href: a string containing the link’s URL.
  meta: a meta object containing non-standard meta-information about the link.

Currently the library supports the first option but not the second. I will be creating a PR for the second, I just wanted to create a ticket to reference first.

[multimeric]

This can probably be closed...?

[GuillaumeCisco]

Is it supported today?
Can't find anything in the documentation :/