Respect userOptions.eslintPath (#195)

if them specify an eslintPath option, and it like a officer eslint folder. he dont have to install the eslint.

README.md

@@ -153,7 +153,8 @@ module.exports = {
 
 #### `eslintPath` (default: "eslint")
 
-Path to `eslint` instance that will be used for linting.
+Path to `eslint` instance that will be used for linting.  
+If the `eslintPath` is a folder like a official eslint, or specify a `formatter` option. now you dont have to install `eslint` . 
 
 ```js
 module.exports = {
@@ -165,7 +166,7 @@ module.exports = {
         exclude: /node_modules/,
         loader: "eslint-loader",
         options: {
-          eslintPath: path.join(__dirname, "reusable-eslint-rules.js"),
+          eslintPath: path.join(__dirname, "reusable-eslint"),
         }
       },
     ],

index.js

@@ -150,13 +150,25 @@ module.exports = function(input, map) {
     loaderUtils.getOptions(webpack)
   )
 
+  var userEslintPath = userOptions.eslintPath
+  var formatter = require("eslint/lib/formatters/stylish")
+
+  if (userEslintPath) {
+    try {
+      formatter = require(userEslintPath + "/lib/formatters/stylish")
+    }
+    catch (e) {
+      formatter = require("eslint/lib/formatters/stylish")
+    }
+  }
+
   var config = assign(
     // loader defaults
     {
-      formatter: require("eslint/lib/formatters/stylish"),
+      formatter: formatter,
       cacheIdentifier: JSON.stringify({
         "eslint-loader": pkg.version,
-        eslint: require(userOptions.eslintPath || "eslint").version,
+        eslint: require(userEslintPath || "eslint").version,
       }),
       eslintPath: "eslint",
     },

test/eslint-path.js

@@ -11,7 +11,7 @@ test.cb("eslint-loader can use another instance of eslint via " +
       entry: "./test/fixtures/good.js",
     },
     {
-      eslintPath: path.join(__dirname, "mock/eslint-mock.js"),
+      eslintPath: path.join(__dirname, "mock/eslint"),
     }
   ),
   function(err, stats) {

test/mock/eslint/lib/formatters/stylish.js

@@ -0,0 +1,3 @@
+module.exports = function(result) {
+  return JSON.stringify(result)
+}