Dependents of this crate and actix-web are broken

[steveej]

Unfortunately #84 broke dependents which also depend on actix-web:

error: failed to select a version for `ring`.
    ... required by package `rustls v0.15.0`
    ... which is depended on by `hyper-rustls v0.16.0`
    ... which is depended on by `dkregistry v0.2.2-alpha.0 (https://github.com/camallo/dkregistry-rs.git?rev=a60d804b697c67b7439522231ccd9179f8334537#a60d804b)`
    ... which is depended on by `graph-builder v0.1.0 (/home/steveej/src/job-redhat/cincinnati/graph-builder)`
versions that meet the requirements `^0.14` are: 0.14.3, 0.14.2, 0.14.1, 0.14.0

the package `ring` links to the native library `ring-asm`, but it conflicts with a previous package which links to `ring-asm` as well:
package `ring v0.13.5`
    ... which is depended on by `cookie v0.11.0`
    ... which is depended on by `actix-web v0.7.18`
    ... which is depended on by `graph-builder v0.1.0 (/home/steveej/src/job-redhat/cincinnati/graph-builder)`

I suggest we revert #84 and actively pursue #44.