Populate templated links directly using resource.

[tobyclemson]

Since halboy is already capable of expanding templated URIs at navigation time, it would be really nice to be able to do the same at read time. For example:

;; { "_links": { "rel": { "href": "https://example.com{?template}", "templated": true } } }
(hal/get-href resource :rel {:template :params}) 
; => "https://example.com?template=params"

[jimmythompson]

Would it make more sense to do this in a separate method, e.g.

(hal/expand-href resource :rel {:template :params})

So you could have a fallback value, e.g.

(hal/get-href resource :rel default)

[tobyclemson]

Yeah, that would work for me :) Can create a PR if you need.