Switch out dplyr dependency for vctrs

[hadley]

dplyr is a user facing package so it's rather dependency heavy in favour of providing the whole package to users. This means it doesn't feel like a great dependency for an SDK, which wants to be low-level. Fortunately, it should be pretty easy to switch out dplyr for vctrs, which is the low-level equivalent, replacing dplyr::bind_rows() with vctrs::vec_rbind().

[nfx]

@hadley what license does vctrs package have? I support the idea of using as little transitive dependencies as possible, though we have to go through approvals for any new packages. e.g. I had to remove configr dep for manual parting of INI file for this same purpose.

[hadley]

It’s MIT.

[nfx]

should be easy to get through, then