Build: .eslintrc -> .eslintrc.json

`.eslintrc` format is deprecated -
http://eslint.org/docs/user-guide/configuring#configuration-file-formats

Fixes gh-3248
Closes gh-3247

dist/.eslintrc.json

@@ -1,5 +1,5 @@
 {
-	"extends": "../src/.eslintrc",
+	"extends": "../src/.eslintrc.json",
 	"rules": {
 		// That is okay for the built version
 		"no-multiple-empty-lines": "off",

src/core.js

@@ -1,5 +1,5 @@
 /* global Symbol */
-// Defining this global in .eslintrc would create a danger of using the global
+// Defining this global in .eslintrc.json would create a danger of using the global
 // unguarded in another place, it seems safer to define global only for this module
 
 define( [

test/node_smoke_tests/.eslintrc.json

@@ -2,6 +2,6 @@
 	"env": {
 		"es6": true
 	},
-	"extends" : "../../.eslintrc",
+	"extends" : "../../.eslintrc.json",
 	"root": true
 }

test/promises_aplus_adapters/.eslintrc

@@ -1,4 +0,0 @@
-{
-	"extends": "../../.eslintrc",
-	"root": true
-}

test/promises_aplus_adapters/.eslintrc.json

@@ -0,0 +1,4 @@
+{
+	"extends": "../../.eslintrc.json",
+	"root": true
+}