Only import used lodash methods

[merceyz]

What's the problem this PR addresses?

• Inquirer is currently loading lodash through the main entrypoint which makes it impossible for webpack to treeshake the unused code.
• Yarn is using Inquirer in its cli and, because of this, is shipping a lot of unnecessary code that we don't need in our bundle.

Compared to the other PRs that attempted to tackle this in the past (https://github.com/SBoudrias/Inquirer.js/pulls?q=is%3Apr+is%3Aclosed+lodash+module) this PR doesn't use the per method packages (they're deprecated and didn't help; https://lodash.com/per-method-packages) but instead requires the used methods directly. This will get rid of unused code and potentially help startup times as there is less code to process.

I made the diff as small as possible which is why I construct a _ object with the used methods. If the project switches to es2015 imports then this can be removed in favour of using https://github.com/lodash/babel-plugin-lodash

How did you fix it?

Imported only the used lodash methods

[merceyz]

Hey @LitoMore 👋, when do you think this will be released?

[LitoMore]

@merceyz I don't have permission to publish on npm, let me contact @SBoudrias for help.

[LitoMore]

@merceyz 7.2.0 released.