Merge with upstream

Author: markmontymark

chapters/classes_and_objects/class-methods-and-instance-methods.md

@@ -5,7 +5,7 @@ chapter: Classes and Objects
 ---
 ## Problem
 
-You want to create a class methods and instance methods.
+You want to create class and instance methods.
 
 ## Solution
 

chapters/classes_and_objects/class-variables.md

@@ -40,4 +40,4 @@ zoo.helpfulInfo()
 
 ## Discussion
 
-Coffeescript will store these values on the class itself rather than on the prototype it defines.  These are useful for defining variables on classes which can't be overridden by instance attribute variables.
+Coffeescript will store these values on the class itself rather than on the prototype it defines.  These are useful for defining variables on classes which can't be overwritten by instance attribute variables.