upgrade to babel 7 and other dependencies

[iAziz786]

This pull request upgrades babel to v7. In order to make everything compatible, I had to upgrade other dependencies as well.

Coverage drops to around 69.23%. @jasonslyvia Can you help to improve it?

Refers to #207

[coveralls]

Coverage decreased (-6.7%) to 69.231% when pulling 158dd74 on iAziz786:upgrade-dependencies into 80bcae4 on jasonslyvia:master.

[coveralls]

Coverage decreased (-6.7%) to 69.231% when pulling 158dd74 on iAziz786:upgrade-dependencies into 80bcae4 on jasonslyvia:master.

[coveralls]

Coverage decreased (-6.7%) to 69.231% when pulling f2081c1 on iAziz786:upgrade-dependencies into 80bcae4 on jasonslyvia:master.

[jasonslyvia]

I'm not quite familiar with the Babel stack now, can you explain why these two plugins are required?

[iAziz786]

Both are official Babel plugins. Since Babel 7, Babel is trying to move to a scope system that's why I have to prefix @babel to the plugin names.

@babel/plugin-syntax-dynamic-import: is used for situations for using dynamic imports import() syntax; I guess I forgot to remove this as we're not doing any.

@babel/plugin-proposal-class-properties: is for new class fields where we can define any property on the class as a regular assignment. This one is required, because, instead of using ::this.handleSomeChange to bind this, I'm using the class fields and arrow functions to do so. The syntax is cleaner and more readable. This may look personal preference but class fields syntax is at stage-3 and more likely to land to JavaScript world whereas :: binding which is at stage-0.

We can write this:

class MyClass {
  ...
  handleSomeChange() {
    doSomething(this.state.value);
  }
  ...
  render() {
    return (
      <button onClick={::this.handleSomeChange}>Click</button>
    )
  }
}

To this:

class MyClass {
  ...
  handleSomeChange = () => {
    doSomething(this.state.value);
  }
  ...
  render() {
    return (
      <button onClick={this.handleSomeChange}>Click</button>
    )
  }
}

I guess that explains why I have added this plugin.
I'm removing @babel/plugin-syntax-dynamic-import because we're not using it anyway; Thanks for pointing out.

[jasonslyvia]

thanks for your excellent explanation!

[jasonslyvia]

I'm okay with the overall change, @ameerthehacker any thoughts?