lint: run errors.js through the linter.
lint: run scanner.js through the linter.
runtime+io: misc lint fixes.
lint: alphabetize some goog.requires.
lint: run datum.js through the linter.
submodule: bump src/js/tdd to get lint fixes.
Makefile: lint all files on pre-commit, not just staged ones.
ast: move {datum, datum_type, sibling_buffer}.js under ast/
eval: rename r5js.Pipeline => r5js.PipelineImpl and move under eval/.
eval: rename r5js.IPipeline => r5js.Pipeline and move under eval/.
runtime: r5js.runtime.UNSPECIFIED_VALUE doesn't need its own class.
Makefile+tutorial: remove tutorial.
misc: remove CHANGELOG and TODO.
test: remove obsolete comment from test_compiled.html.