Check for "dependencies" and "peerDepenendencies"

Fix for following issues:

- eslint/eslint#3458
- eslint/eslint#2518

package.json

@@ -20,6 +20,9 @@
     "lodash": "^4.13.1",
     "mocha": "^2.4.5"
   },
+  "peerDependencies": {
+    "eslint-plugin-promise": "^1.3.2"
+  },
   "engines": {
     "node": ">=4"
   },

test/index.js

@@ -12,6 +12,15 @@ function runEslint ( code, configFile ) {
 	});
 }
 
+describe('Dependencies', function () {
+
+	it('all "dependencies" are defined in "peerDependencies"', function () {
+		var pkg = require('../package.json');
+		assert.deepStrictEqual(pkg.dependencies, pkg.peerDependencies);
+	});
+
+});
+
 describe('Config format', function () {
 
 	var config = require('../');