Refactor docs into mdbook (#547)

* Refactor documentation, ef_tests makefile

* Add makefile to root

* Tidy readme

* Fix readme badges

* Tidy logs

* Add terminalize gif

* Update readme image

* Update readme image

* Tidy logs

* Update readme image

* Update readme

* Update readme

* Fix book link

* Update makefiles

* Update book

* Fix link in book

* Add readme for book

* Remove old docs, move api spec YAML

* Fix eth2/ dir readme

* Add readme for lcli

* Add about this book section

* Minor formatting improvements

* Address mehdi's comments

tests/ef_tests/README.md

@@ -0,0 +1,30 @@
+# Ethereum 2.0 Specification Tests
+
+This crate parses and executes the test vectors at [ethereum/eth2.0-spec-tests](https://github.com/ethereum/eth2.0-spec-tests).
+
+Functionality is achieved only via the `$ cargo test` command.
+
+## Tests
+
+Because the test vectors are very large, we do not download the
+tests vectors or require that the tests pass by default. Specifically;
+
+- If the `tests/ef_tests/eth2.0-spec-tests` directory is not present, all tests
+	indicate a `pass` when they did not actually run.
+- If that directory _is_ present, the tests are executed faithfully, failing if
+	a discrepancy is found.
+
+## Downloading Test Vectors
+
+The `eth2.0-spec-tests` directory is not present by default. To
+obtain it, use the Makefile:
+
+```
+$ make
+```
+
+_Note: this may download hundreds of MB of compressed archives from the
+[ethereum/eth2.0-spec-tests](https://github.com/ethereum/eth2.0-spec-tests/),
+which may expand into several GB of files._
+
+Remove the tests to save space or update to a new version with `$ make clean`.