Publish ssz_types (and deps) to crates.io (#468)

* Rename `hashing` crate to `eth2_hashing`

* Add license, desc to eth2_hashing Cargo.toml

* Remove merkle root from eth2 hashing

* Remove old benches folder (zombied from old branch)

* Add docs to eth2_hashing

* Prepare tree_hash for publishing on crates.io

* Update deps to use crates.io instead of paths

* Update all crates to pull ssz from crates.io

* Remove cached_tree_hash, add patches to manifest

* Fix compile error in benches

* Remove unused code

* Fix fake_crypto compile error

eth2/utils/eth2_hashing/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "eth2_hashing"
+version = "0.1.0"
+authors = ["Paul Hauner <paul@paulhauner.com>"]
+edition = "2018"
+license = "Apache-2.0"
+description = "Hashing primitives used in Ethereum 2.0"
+
+[target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+ring = "0.14.6"
+
+[dev-dependencies]
+rustc-hex = "2.0.1"
+
+[target.'cfg(target_arch = "wasm32")'.dev-dependencies]
+wasm-bindgen-test = "0.2.47"