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/merkle_proof/Cargo.toml

@@ -6,4 +6,4 @@ edition = "2018"
 
 [dependencies]
 ethereum-types = "0.6"
-hashing = { path = "../hashing" }
+eth2_hashing = { path = "../eth2_hashing" }