* Update to spec v0.9.0
* Update to v0.9.1
* Bump spec tags for v0.9.1
* Formatting, fix CI failures
* Resolve accidental KeyPair merge conflict
* Document new BeaconState functions
* Fix incorrect cache drops in `advance_caches`
* Update fork choice for v0.9.1
* Clean up some FIXMEs
* Fix a few docs/logs
* Change reduced tree for adding weightless node
* Add more comments for reduced tree fork choice
* Small refactor on reduced tree for readability
* Move test_harness forking logic into itself
* Add new `AncestorIter` trait to store
* Add unfinished tests to fork choice
* Make `beacon_state.genesis_block_root` public
* Add failing lmd_ghost fork choice tests
* Extend fork_choice tests, create failing test
* Implement Debug for generic ReducedTree
* Add lazy_static to fork choice tests
* Add verify_integrity fn to reduced tree
* Fix bugs in reduced tree
* Ensure all reduced tree tests verify integrity
* Slightly alter reduce tree test params
* Add (failing) reduced tree test
* Fix bug in fork choice
Iter ancestors was not working well with skip slots
* Put maximum depth for common ancestor search
Ensures that we don't search back past the finalized root.
* Add basic finalization tests for reduced tree
* Change fork choice to use beacon_block_root
Previously it was using target_root, which was wrong
* Make ancestor iter return option
* Disable fork choice test when !debug_assertions
* Fix type, removed code fragment
* Tidy some borrow-checker evading
* Lower reduced tree random test iterations
