* Add pnet protocol
copied from plaintext protocol, since that seems to be the closest match
* Minimalize the pnet protocol
* WIP private swarms with fixed key
* Different nonces for write and read
* Use per stream write buffer to avoid allocations
* Add parsing and formating of PSKs
* Directly call handshake
Also remove unneeded InboundUpgrade and OutboundUpgrade
* Add HandshakeError
* Add dedicated pnet example
* Add tests for PSK parsing and formatting
* Some more tests for the parsing, fail case
* Add fingerprint
To be able to check if a go-ipfs and rust-libp2p use the same key without
having to dump the actual key. Not sure if there is a spec for this anywhere,
but it is basically just copied from go-ipfs.
* Minimize dependencies and remove dead code
* Rename PSK to PreSharedKey and use pin_project
* Add crypt_writer
Basically a stripped down and modified version of async_std BufWriter that
also encrypts using the given cipher.
* cargo fmt
* Actually get rid of the Unpin requirement
* Rewrite flushing and remove written count from state
* Add docs for pnet/lib.rs
* Increase library version
* Remove pnet example
There will be a more elaborate and useful example in a different PR
* Return pending on pending...
also make doc text less ambiguous
* Add debug assertions to check invariants of poll_flush_buf
Also, clarify the invariants in the comments of that method
