Add nested property setting

[runningskull]

get()ing nested properties using dot-notation works, so it seems logical that it should work during set() as well. I needed it today, so implemented it.

It behaves like a mkdir -p, creating objects along the path if they don't exist. The other option is to throw in error in that case. I haven't thought through the pros/cons of each.

If this is a desired feature, I'll happily add some tests & polish it up.

EDIT: fixed a bug

[defunctzombie]

Any prior art with other view/bindings frameworks and what they do? This seems like a reasonable feature.

[yanatan16]

:+1: lgtm

[defunctzombie]

Can merge after tests added.