[npm] move jshint to peerDependencies

Special versions of jshint are currently supported via the [`linter` config option](https://github.com/spalger/gulp-jshint#options), but with this change jshint is something you would install along with gulp-jshint.

README.md

@@ -18,7 +18,7 @@
 
 ## Install
 
-    npm install gulp-jshint --save-dev
+    npm install jshint gulp-jshint --save-dev
 
 ## Usage
 

package.json

@@ -14,12 +14,14 @@
   ],
   "dependencies": {
     "gulp-util": "^3.0.0",
-    "jshint": "^2.7.0",
     "lodash": "^3.0.1",
     "minimatch": "^2.0.1",
     "rcloader": "0.1.2",
     "through2": "~0.6.1"
   },
+  "peerDependencies": {
+    "jshint": "2.x"
+  },
   "devDependencies": {
     "gulp": "^3.8.10",
     "mocha": "^2.1.0",