new Buffer is deprecated and unsafe

[ghost]

This PR replaces all new Buffer with Buffer.from. We should not use Buffer constructor which is deprecated and unsafe.

The behavior of new Buffer() is different depending on the type of the first argument, security and reliability issues can be inadvertently introduced into applications when argument validation or Buffer initialization is not performed.

To make the creation of Buffer instances more reliable and less error-prone, the various forms of the new Buffer() constructor have been deprecated and replaced by separate Buffer.from(), Buffer.alloc(), and Buffer.allocUnsafe() methods.

Check this out: https://nodejs.org/api/buffer.html#buffer_buffer_from_buffer_alloc_and_buffer_allocunsafe
https://github.com/nodejs/Release#end-of-life-releases

[coveralls]

Coverage remained the same at 83.169% when pulling 65dc0c3 on noelyoo:1.0 into 0de98a5 on ethereum:1.0.

[nivida]

I've already fixed the Buffer usage in the PR #2000. 🙈