Use AST selector for no-new-buffer rule

[SamVerschueren]

Looks cleaner with a selector.

[jfmengels]

You're right, it looks better with selectors. But the plugin currently has a peer dependency to ESLint >= 3.6, whereas AST selectors landed in ESLint 3.18.0. So landing this would break this rule for any projects using ESLint < 3.18.0 :/

[sindresorhus]

@SamVerschueren Can you bump the peerDependency to ESLint v4? We'll have to do a major version anyways (because of new default rules).

[SamVerschueren]

Done