Establish relationship to com crate

@kennykerr and I have had some conversations about the relationship of  this crate to the [com crate](https://github.com/microsoft/com-rs). Most of the functionality of the com crate will be subsumed by this crate. The question does remain whether there will be a need for higher level COM helpers that should live in a separate COM crate or whether the com crate should be completely deprecated. 