Is interesting to have an only option to iterate in epecific array?

[guilhermegazzinelli]

Firstly, thanks for the fantastic work in this gem.

In our Use-case, we had to implement an only option to the gem.

Consider you want choose specifics dates, and want to preserve the use of montrose to give next iterations and leverage all useful methods, that's not possible in current version.

We coded this feature in our fork, and maybe it's interesting for the project.
You think this relevant to in the gem?

I can make a PR to have this ported to Montrose, ensuring documentations and tests if it seems a good feature.