Allow paths to contain `*`
Allow paths to contain `*`

From #377, the [TUF spec] allows for paths to contain `*`. According to
@lukesteensen, this is routinely used in delegations.

Note though this does not attempt to implement delegation path globs.
That will be implemented in #388.

[TUF spec]: https://theupdateframework.github.io/specification/latest/#targetpath

heartsucker/rust-tuf,heartsucker/rust-tuf,heartsucker/rust-tuf