tools: add eslint rule prefer-assert-methods

PR-URL: https://github.com/nodejs/node/pull/8622
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Yorkie Liu <yorkiefixer@gmail.com>
Reviewed-By: Jackson Tian <shvyo1987@gmail.com>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Teddy Katz <teddy.katz@gmail.com>

test/parallel/test-https-byteswritten.js

@@ -18,7 +18,7 @@ var body = 'hello world\n';
 
 var httpsServer = https.createServer(options, function(req, res) {
   res.on('finish', function() {
-    assert(typeof req.connection.bytesWritten === 'number');
+    assert.strictEqual(typeof req.connection.bytesWritten, 'number');
     assert(req.connection.bytesWritten > 0);
     httpsServer.close();
     console.log('ok');