fix up let scoping transformer comments

lib/6to5/transformation/transformers/let-scoping.js

@@ -132,7 +132,7 @@ LetScoping.prototype.run = function () {
 
 /**
  * There are no let references accessed within a closure so we can just traverse
- * through this block and replace all references that exist in a high scope to
+ * through this block and replace all references that exist in a higher scope to
  * their uids.
  */
 
@@ -211,7 +211,8 @@ LetScoping.prototype.getInfo = function () {
 /**
  * If we're inside of a `For*Statement` then traverse it and check if it has one
  * of the following node types `ReturnStatement`, `BreakStatement`,
- * `ContinueStatement` and replace it with a return value we can track later on.
+ * `ContinueStatement` and replace it with a return value that we can track
+ * later on.
  *
  * @returns {Object}
  */
@@ -251,7 +252,7 @@ LetScoping.prototype.checkFor = function () {
 
 /**
  * Hoist all var declarations in this block to before it so they retain scope
- * once we wrap everything is in a closure.
+ * once we wrap everything in a closure.
  */
 
 LetScoping.prototype.hoistVarDeclarations = function () {