rename Scope.init to Scope.crawl

lib/6to5/traverse/scope.js

@@ -30,7 +30,7 @@ function Scope(block, parentBlock, parent, file) {
   this.parentBlock = parentBlock;
   this.block       = block;
 
-  this.init();
+  this.crawl();
 }
 
 Scope.defaultDeclarations = flatten([globals.builtin, globals.browser, globals.node].map(Object.keys));
@@ -246,7 +246,7 @@ var blockVariableVisitor = {
   }
 };
 
-Scope.prototype.init = function () {
+Scope.prototype.crawl = function () {
   var parent = this.parent;
   var block  = this.block;
   var i;