Release 0.7.0-alpha.4 (#551)

* update: types

* downgrade: rust toolchain

* update: ss58 printer

* update: crab runtime

* update: darwinia runtime

* fix compile and update version

* bump: dependencies

* update: tron backing genesis

* reorder

* remove: unused comment

* build: spec

Co-authored-by: HackFisher <hackfisher@gmail.com>

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
       - name: Install latest nightly
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: nightly
+          toolchain: nightly-2020-09-20
           override: true
           target: wasm32-unknown-unknown