Upgrade generator

[UlisesGascon]

We can upgrade the generator a little bit 💪 💪

Important!

• The current working branch for this job is development. Please point the PRs to that branch

Asigned tasks

• Migrate to ES6+ (lead @KoolTheba) Tests migrated to ES6 #240 Tests migrated to ES6 #219
• Upgrade dependency yeoman-generator to ^4.2.0. Major code change (lead @KoolTheba)

Some ideas (free to pick):

• Reduce support for lower Nodejs versions (I suggest to support from v10 (included))
• Upgrade dependency yeoman-test to 2.0.0
• Upgrade dependency yeoman-assert to ^3.1.1
• Upgrade dependency generator-jasmine to ^2.0.1
• Upgrade dependency generator-mocha to ^2.0.3

🚀 More ideas are super welcome!.

This issue is great for newcomers and first contributions, so... don't be shy and let us know if you want to help us 😉

[KoolTheba]

Hi folks!
I'd love to help with this issue. I can take care of the ES6 migration and the upgrade dependency for Yeoman generator.

[UlisesGascon]

Thanks @KoolTheba! I asigned you the tasks you requested

[HemantPawar]

TLDR: Generated extensions will work but Chrome webstore will not approve the generated extensions.

A lot of things have changed over the past few years.

Chrome webstore now doesn't approve extension with bundler generated/obfuscated code. So we may have to drop babel, gulp, bower, uglify etc.

Also, this generator was built a long time ago when Chrome was on ES5. But now Chrome supports ES6+ and modules. So we can safely drop some dependencies as well.

[HemantPawar]

Here is the related snippet from Developer Program Policies

Code Readability Requirements:
Developers must not obfuscate code or conceal functionality of their extension. 
This also applies to any external code or resource fetched by the extension package. 
Minification is allowed, including the following forms:

- Removal of whitespace, newlines, code comments, and block delimiters
- Shortening of variable and function names
- Collapsing files together