Add lost documentation for di-unused to README.md

Author: tilmanschweitzer

README.md

@@ -174,6 +174,7 @@ Users may use the shareable [eslint-config-angular](https://github.com/dustinspe
 | definedundefined          | You should use the angular.isUndefined or angular.isDefined methods instead of using the keyword undefined. We also check the use of !angular.isUndefined and !angular.isDefined (should prefer the reverse function)|
 | di                        | All your DI should use the same syntax : the Array or function syntaxes ("di":  [2, "function or array"])|
 | di-order                  | Injected dependencies should be sorted alphabetically. If the second parameter is set to false, values which start and end with an underscore those underscores are stripped. This means for example that `_$httpBackend_` goes before `_$http_`. |
+| di-unused                 | Unused dependencies should not be injected. |
 | directive-name            | All your directives should have a name starting with the parameter you can define in your config object. The second parameter can be a Regexp wrapped in quotes. You can not prefix your directives by "ng" (reserved keyword for AngularJS directives) ("directive-name":  [2, "ng"]) [Y073](https://github.com/johnpapa/angular-styleguide#style-y073), [Y126](https://github.com/johnpapa/angular-styleguide#style-y126) |
 | directive-restrict        | Not all directive restrictions may be desirable. Also it might be desirable to define default restrictions, or explicitly not. The default configuration limits the restrictions `AE` [Y074](https://github.com/johnpapa/angular-styleguide#style-y074) and disallows explicitly specifying a default. ("directive-restrict": [0, {"restrict": "AE", "explicit": "never"}]) |
 | document-service          | Instead of the default document object, you should prefer the AngularJS wrapper service $document. [Y180](https://github.com/johnpapa/angular-styleguide#style-y180) |