update babel to version 7

[achmadk]

Fixed #21 issue.

[coveralls]

Coverage increased (+10.3%) to 100.0% when pulling 45283f2 on achmadk:master into a190d07 on aichbauer:master.

[coveralls]

Coverage increased (+10.3%) to 100.0% when pulling f89a2ce on achmadk:master into a190d07 on aichbauer:master.

[coveralls]

Coverage increased (+10.3%) to 100.0% when pulling 45283f2 on achmadk:master into a190d07 on aichbauer:master.

[aichbauer]

Thanks for your contribution... Looks good... Just one little thing.

Also when we want to merge this you need to drop the node version 4 in the travis file.

[aichbauer]

We should move the @babel/* dependencies to devdependencies except of @babel/runtime.

[achmadk]

I have tried to move that @babel/* dependencies to devDependencies, but it will give an error when execute npm run test

[aichbauer]

Try moving these to devDependencies:

    "@babel/cli": "^7.0.0",
    "@babel/core": "^7.0.0",
    "@babel/plugin-transform-runtime": "^7.0.0",
    "@babel/preset-env": "^7.0.0",

and keep this as dependencies:

    "@babel/register": "^7.0.0",
    "@babel/runtime": "^7.0.0",

[aichbauer]

in the travis.yml you need to remove node version 4.

node_js:
  - 4
  - 6
  - 8
  - 10

to

node_js:
  - 6
  - 8
  - 10