lint,deps: move ESLint config to separate package

Move ESLint configuration to a separate package
(`eslint-config-metarhia`).  Also, bump ESLint to 4.6.1 (from 4.6.0)
because that's what's specified in that package's peerDependencies.

PR-URL: metarhia/jstp#302
Reviewed-By: Denys Otrishko <shishugi@gmail.com>
Reviewed-By: Dmytro Nechai <nechaido@gmail.com>
Reviewed-By: Mykola Bilochub <nbelochub@gmail.com>

.eslintrc

@@ -0,0 +1,3 @@
+{
+  "extends": "metarhia"
+}