ES6 refactoring

[JPeer264]

I refactored some files to ES6 according to #355 . Much things are not available in Node v4.

'use strict' is a must in Node v4 if let is used. For consistency I also put it although no let is used.

[coveralls]

Coverage decreased (-0.02%) to 85.121% when pulling 01c96fe on JPeer264:feature/refactor-es6 into 108b88a on jprichardson:master.

[RyanZim]

'use strict' isn't required for let in Node 4 (http://node.green/#let), but it's a good practice anyway.

[RyanZim]

@JPeer264 Thanks for doing this!

If you feel like refactoring other parts (including tests), you are more than welcome to. 😸

[JPeer264]

'use strict' isn't required for let in Node 4 (http://node.green/#let), but it's a good practice anyway.

@RyanZim I read this too but my shell output told me something else. Also it is just with let:

let mkdir = require('../mkdirs')
^^^

SyntaxError: Block-scoped declarations (let, const, function, class) not yet supported outside strict mode
    ...

Thanks. I will first finish all other parts (including README) and start with all tests, if that is ok 👍

[RyanZim]

my shell output told me something else

Strange. My test:

$ node -v
v4.5.0
$ node
> let a = 4
undefined
> a
4

All files should be in strict mode anyhow, so don't worry about it.

[JPeer264]

In the shell directly it works fine for me as well. But not if you run it from a file:

$ node -v
v4.7.3
$ echo "let a = 1" >> foo.js && node foo.js

[RyanZim]

Huh, never knew that.