* Use parity-crypto updated to use upstream rust-secp256k1
* Fetch dependency from git
* Missed a session ID
* Add free-standing inversion function that uses `libsecp256k1`
* fixed tests
* Update deps
* Use parity-crypto 0.5.0
Use libsecp256k1 0.3.5
* Review grumble
Co-authored-by: Svyatoslav Nikolsky <svyatonik@gmail.com>