Introduce toy runtime for testing inside substrate. (#66)

* Introduce simple blockchain runtime for substrate tests.

* Remove bad files.

* Add needed wasm binaries.

* Refactoring.

- Repot files in test-runtime.
- Rename troublesome `Joiner::join` to `Joiner::and`.
- Rework `Slicable` to dedup code.

* More fixes and refactoring

* Rebuild substrate test wasm.

* Fix merge errors.

* Rename the disasterously named `to_vec` to `encode`.

Also rename `as_slice_then` to `with_encoded`.

* Tests for toy runtime.

* Fix doc nit

polkadot/runtime/wasm/Cargo.lock

@@ -395,6 +395,7 @@ dependencies = [
  "substrate-primitives 0.1.0",
  "substrate-runtime-io 0.1.0",
  "substrate-runtime-std 0.1.0",
+ "substrate-runtime-support 0.1.0",
 ]
 
 [[package]]
@@ -638,6 +639,19 @@ dependencies = [
  "rustc_version 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "substrate-runtime-support"
+version = "0.1.0"
+dependencies = [
+ "environmental 0.1.0",
+ "hex-literal 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "substrate-codec 0.1.0",
+ "substrate-primitives 0.1.0",
+ "substrate-runtime-io 0.1.0",
+ "substrate-runtime-std 0.1.0",
+ "substrate-state-machine 0.1.0",
+]
+
 [[package]]
 name = "substrate-state-machine"
 version = "0.1.0"