Additional runtime tests for the test-runtime (#69)

* Remove rustc dependency from ed25519 and refactor a little.

* Runtime support provides more extensive test-key functionality.

* Additional APIs for ed25519 stuff.

* Extensive test for test-runtime.

* Fixes for the new test key API.

* Additional convenience for tests

* Take advantage of more convenient API.

* Redo formating.

* Remove old test identities.

* Remove boilerplate, add test.

* Refactor out unneeded code.

* Clean up algo for determining authorities.

* Remove unneeded API.

* Make `to_*` consume

* Only export keyring when testing

* Fix build & warning

* Extract Keyring into separate library.

* Add tests for Keyring and a trait-based API.

* Address grumbles.

polkadot/runtime/wasm/Cargo.lock

@@ -92,8 +92,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 name = "ed25519"
 version = "0.1.0"
 dependencies = [
+ "hex-literal 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ring 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "rustc-hex 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "substrate-primitives 0.1.0",
  "untrusted 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -643,6 +643,7 @@ dependencies = [
 name = "substrate-runtime-support"
 version = "0.1.0"
 dependencies = [
+ "ed25519 0.1.0",
  "environmental 0.1.0",
  "hex-literal 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "substrate-codec 0.1.0",