Update todo

todo.md

@@ -1,18 +1,20 @@
 TODO
 ====
 
-* Complete javascript and golang grammars
-* Make separator character set configurable, not hard-coded to whitespace
+Backlog
+-------
+
+* Complete the golang grammar
+* Implement the remainder of the incremental parsing algorithm: reuse parse tree after the edit
+* Add API for iterating over a document's tokens
+* Add API for locating a node given a character position
+* Add API for locating a node's parents and siblings
+* Make parse error handling more robust
 * Add special lexical behavior for indentation-aware languages
-* Return a useful error when grammar contains invalid regex patterns
-* Create working parser when grammar contains no error productions
-* Create working parser when grammar contains unused symbols
+* Speed up grammar compilation
+
+Icebox
+------
+
 * Implement Pager's [Practical general method](http://link.springer.com/article/10.1007%2FBF00290336)
   for reducing the size of the LR(1) parse table
-* Speed up grammar compilation
-* Implement the remainder of the incremental parsing algorithm: reuse parse
-  tree after the edit
-* Create easy way to publish grammars as npm packages
-* Add simple selector engine for syntax trees
-* Make ordering of parse and lex tables deterministic, so that generated
-  code doesn't keep changing on every commit