Bump version to 0.16.0

We just updated the rustls dependency, in order for downstream crates to
take advantage of this change bump the version so we can release.

Author: tcharding

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "electrum-client"
-version = "0.15.1"
+version = "0.16.0"
 authors = ["Alekos Filini <alekos.filini@gmail.com>"]
 license = "MIT"
 homepage = "https://github.com/MagicalBitcoin/rust-electrum-client"