fix tests so failures report the right line number
update tests to use DocField.apply
Nicer toStrings for physical plan (Fixes #125)
emit ADT constructors for selectors in RenderTree
Now that we have a separate mechanism to get the JavaScript form, this seems more useful
prefix ExprOp toStrings
prettify Sort toString
prefix Selector toStrings
fix parsing of ">="
Tests for order by with nested fields (Fixes #53)
implementation not changed, tests did not turn up any problems
test for nested projection in order by
refactor MongoDBEvaluator to make the logic reusable
use MongoDBEvaluator to convert physical plan to JS (Fixes #111)