fix broken code, lint and codestyle fixes

lib/6to5/transformation/transformers/es6/tail-call.js

@@ -2,7 +2,6 @@
 
 var util = require("../../../util");
 var t    = require("../../../types");
-var _    = require("lodash");
 var map  = require("lodash/collection/map");
 var flatten = require("lodash/array/flatten");
 var reduceRight = require("lodash/collection/reduceRight");
@@ -86,11 +85,11 @@ TailCallTransformer.prototype.run = function () {
   var body = t.ensureBlock(node).body;
 
   if (this.vars.length > 0) {
-    var declarations = flatten(map(this.vars, function(decl) {
-      return decl.declaration;
-    }));
-    var statement = reduceRight(declarations, function(expr, decl) {
-      return t.assignmentExpression("=", decl.id, expr)
+    var declarations = flatten(map(this.vars, function (decl) {
+      return decl.declarations;
+    }, this));
+    var statement = reduceRight(declarations, function (expr, decl) {
+      return t.assignmentExpression("=", decl.id, expr);
     }, t.identifier("undefined"));
     body.unshift(t.expressionStatement(statement));
   }

lib/6to5/traversal/scope.js

@@ -317,7 +317,6 @@ var blockVariableVisitor = {
 };
 
 Scope.prototype.crawl = function () {
-  var parent = this.parent;
   var block  = this.block;
   var i;
 

lib/6to5/types/index.js

@@ -1,7 +1,6 @@
 "use strict";
 
 var toFastProperties = require("../helpers/to-fast-properties");
-var defaults         = require("lodash/object/defaults");
 var isString         = require("lodash/lang/isString");
 var compact          = require("lodash/array/compact");
 var esutils          = require("esutils");