Remove outstanding todo

There was one todo left to implement maxExpandFrames which was done in
PR #85.

Fixes #9.

lib/state.js

@@ -198,8 +198,6 @@ StateResolver.prototype.trimVariableTable_ = function(fromIndex, frames) {
 };
 
 StateResolver.prototype.resolveFrames_ = function() {
-  // TODO(ofrobots): only gather variables for top n frames (python: 5)
-
   var frames = [];
   var frameCount = Math.min(this.state_.frameCount(),
     this.config_.capture.maxFrames);