Use the exsisting link collection when properties are links.

This seems to be the espected behaviour, as every other link uses
the 'relation' property of the link. Also allows resources to contain
an embedded resource and a link with the same name.
Allow resource properties to be LinkCollections.

Any LinkCollection is merged with the created resource's links.
Merge pull request #8 from BeckonCall/hydrator-links

Use the exsisting link collection when properties are links.
[#8] Remove redundancies

- Pull link collection from resource early so it can be operated on directly
- Remove check for Link objects when iterating over LinkCollection
- Simplify assignment of normalized links to resource representation
Merge branch 'hotfix/8'

Close #8