Cache reader in sgGrammarReader directive
Add keybindings in sg.json
Fix typo in state.initKeyCaptures()
Fix adposition sections in sg_labels.json
Refactor Range
Add Range.toArray()
Select what we want in sgGrammarRetriever

Buggy, expensive - needs refactoring...
Fix in sgGrammarRetriever

Weird - the selectors don't work when it's the other way around. Not
entirely sure why.
Fix in sgGrammarReader directive

Call the right function to clear the reader.