Rename repository from core to rand_core?

[newpavlov]

Having a repository named differently form the crate can be a bit confusing, especially considering that core usually used for libcore. Additionally, the current name is not consistent with the already existing rand_distr repository.

[newpavlov]

@dhardy @josephlr @vks WDYT?

[josephlr]

Changing name is fine by me. My guess is that most people will find the repository via the crates.io/docs.rs repository metadata, so it shouldnt be too bad either way.

[dhardy]

I guess it's not too late to change the name (we only have a pre-release out, plus a few links in this repo and the rand repo to update).

My reasoning for using just core was to minimize redundancy in the name, but the full rand_core is more clear. 👍