Allowing using `NamedTuple` as `initial_params`

[torfjelde]

Ref: https://github.com/TuringLang/Turing.jl/issues/2286

Quick and dirty implementation, but does the trick.

I probably shouldn't spend much time on this (have other PRs that I need to complete), but figured I'd just add this here in case someone else wants to complete it (maybe @sunxd3 or @mhauru has time) :)

Basically, it's just missing:

• [x] Testing

[sunxd3]

Looks reasonable, maybe we can just move update_values!! to out into utils.jl. Regardless, I can write some tests for this.

Can I get your permission to just commit to this PR? @torfjelde

[torfjelde]

Looks reasonable, maybe we can just move update_values!! to out into utils.jl.

Indeed:)

Can I get your permission to just commit to this PR? @torfjelde

Yep, go for it!

[coveralls]

Pull Request Test Coverage Report for Build 10038614257

Details

• 20 of 24 (83.33%) changed or added relevant lines in 3 files are covered.
• 13 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.05%) to 81.36%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/sampler.jl	16	17	94.12%
src/varinfo.jl	0	3	0.0%
<!--	Total:	20	24	83.33%	-->

Files with Coverage Reduction	New Missed Lines	%
src/model.jl	1	87.0%
src/threadsafe.jl	12	45.19%
<!--	Total:	13		-->

Totals
Change from base Build 10038508405:	-0.05%
Covered Lines:	2811
Relevant Lines:	3455

---

💛 - Coveralls

[torfjelde]

LGTM:) Unfortunately I seems I can't approve because I'm the creator of the PR 🙃

[sunxd3]

wait till https://github.com/TuringLang/DynamicPPL.jl/pull/626 to merge, then I'll fix the versioning and potential errors

[sunxd3]

Do we need to make this breaking? If not, we can combine the release with https://github.com/TuringLang/DynamicPPL.jl/pull/626