Added QueryResult and patched bugs

QueryResult now stores result items and position data, which aligns more
strongly with the rest of the library features than a plain
[]interface[}.  The design of the parser_test unittest was revised to
use array/map/scalar serialization (like match_test), since Go 1.3
redesigned maps to randomly order their keys. Since naive comparisons of
map data is now no longer possible, the unittest now sorts map
keys:value combinations.

* Patched a bug where getPosition("") was returning an invalid Position
* Revised parser_test to use serialization for comparisons for Go 1.3

jpath/match.go

@@ -28,7 +28,7 @@ func (f *terminatingFn) SetNext(next PathFn) {
 }
 
 func (f *terminatingFn) Call(node interface{}, ctx *queryContext) {
-	ctx.appendResult(node)
+	ctx.result.appendResult(node)
 }
 
 // shim to ease functor writing