Merge pull request astaxie#795 from ZhenhangTung/master

fix interface implementation of student and employee

Author: astaxie

en/02.6.md

@@ -14,7 +14,7 @@ Let's do some more work. We'll add one more method `Sing()` to them, along with
 
 Now, Student has three methods called `SayHi()`, `Sing()` and `BorrowMoney()`, and Employee has `SayHi()`, `Sing()` and `SpendSalary()`.
 
-This combination of methods is called an interface and is implemented by both Student and Employee. So, Student and Employee implement the interface: `SayHi()` and `Sing()`. At the same time, Employee doesn't implement the interface: `SayHi()`, `Sing()`, `BorrowMoney()`, and Student doesn't implement the interface: `SayHi()`, `Sing()`, `SpendSalary()`. This is because Employee doesn't have the method `BorrowMoney()` and Student doesn't have the method `SpendSalary()`.
+This combination of methods is called an interface and is implemented by both Student and Employee. So, Student and Employee implement the interface: `SayHi()` and `Sing()`. At the same time, Employee doesn't implement the interface: `BorrowMoney()`, and Student doesn't implement the interface: `SpendSalary()`. This is because Employee doesn't have the method `BorrowMoney()` and Student doesn't have the method `SpendSalary()`.
 
 ### Type of Interface