"Exercise 2: Class" only run on strict mode

[danielortiz]

Tried to run my program with "tower-of-babel run program.js" and nothing happened, then I ran "babel-node program.js 2 3" and received the message "SyntaxError: Block-scoped declarations (let, const, function, class) not yet supported outside strict mode"

Added "strict mode" and all went well, but I think it'd be good to mention that on the lesson.

[yosuke-furukawa]

Thanks.
But that problem is occurred from bable-node v6. bable-node does not transpiled ES2015 class by default.
I guess you need to add .babelrc file and write the following definitions.

{
  "plugins": ["transform-es2015-classes"]
}