* Add an optional configuration for Rocket.toml, ca_certs, to take
  in a directory and use it for MTLS.
* Update Cargo.toml to point to fork of hyper-sync-rustls with updates
  for MTLS.

* Save peer certificates from network stream to Data
* Add peer_certs field to Request
* Move certificates from Data to Request

* Lookup domain name associated with client's IP Address.
* Verify that the domain name match the certificate common name.

* Clean up code.
* Added better comments.

* Make cert_store_path optional.
* Modify code sample to reflect changes.

* Move mtls.rs contents into tls.rs.
* Parse certificat into MutualTlsUser.
* Create getter methods for MutualTlsUser.
* Generate MutualTlsUser from first accepted certificate from
  array the client provides.

* Add more comments explaining sections of code.
* Add documentation and examples.
* Remove public key and signature from MutualTlsUser.
* Improve error handling to not panic when generating a new
  MutualTlsUser.
* Replace unwraps with exceptions to specify what failed.

* Combine lines of code that can be together and simplify
  get_not_before and get_not_after method names.
* Remove methods referenced in comments that are no longer
  implemented.

* Use combinators instead of explicit matches where possible
* Remove some clone() calls
* Return references instead of copies

This keeps the internals of the name validation out of the
`from_request` logic for `MutualTlsUser`, which is currently still in
the core rocket lib to avoid circular dependencies.

Even without exposing the certificate details, MutualTlsUser provides a
guard that only allows authenticated clients to connect. Removing the
certificate parsing will allow this functionality to be added before all
the details of parsing the certificates have been figured out.

* Remove all fields and methods from MutualTlsUser
* Remove openssl dependency
* Update tests

This is not necessarily the value stored in the subject name of the
certificate, but it is the name for which the provided certifcate was
validated.