Update minimum Node version on README.md

[luixxiul]

Describe the issue you encountered: Update minimum Node version on README.md.

With v7.3.0 I got an unit test error, which is:

  1444 passing (17s)
  47 pending
  1 failing

  1) downloadsBar component very narrow downloads bar with items renders no downloads:

      AssertionError: 3 == 0
      + expected - actual

      -3
      +0
      
      at Context.<anonymous> (test/unit/app/renderer/components/download/downloadBarTest.js:118:14)

The error was fixed by updating Node to v7.9.0.

We could update it to 8 instead of it, though I am not sure if the browser is fully compatible with that newer version.

• Platform (Win7, 8, 10? macOS? Linux distro?): macOS

• Brave Version (revision SHA): master

• Steps to reproduce:

  1. git push

• Extra QA steps:
  1.
  2.
  3.

• Any related issues:

[luixxiul]

Let's decide the version number soon, since there might be a chance where other contributors also experience the bug.

[bsclifton]

I think it's safe to recommend 7.9.0 (or newer) 👍

We can now also remove this part:

2. node-gyp 3.3.1

 sudo npm install -g node-gyp@3.3.1

and update
Install the Node (v5+) dependencies:
to
Install the Node dependencies:

[luixxiul]

It is ok to remove node-gyp though there are several files where node-gyp seems to be called?

[luixxiul]

https://github.com/brave/browser-laptop/search?utf8=%E2%9C%93&q=node-gyp&type=

[bsclifton]

@luixxiul correct, you can remove the global instance... because we already include it as a module in our package.json:

browser-laptop/package.json

Line 176 in ed19951

"node-gyp": "^3.2.1",

I don't think it was ever needed to be installed globally. I haven't had it installed in over a year

[luixxiul]

I see. I'm going to create a PR.