Fix documentation and README

[khorolets]

I've noticed that the README I wrote lies in a couple of places, like using async where it's not necessary or using some near-* crates either has changed or was initially wrong.

It needs to be reviewed and fixed to avoid misleading people.

[dj8yfo]

@khorolets it should be all good now, besides probably this section

[khorolets]

@dj8yfo