docs(README): remove duplicate (Options) (#51)

Author: pierreneter

README.md

@@ -71,12 +71,11 @@ This plugin supports UglifyJS features as discussed below:
 | beautify | boolean | false | Beautify output. |
 | output | An object providing options for UglifyJS [OutputStream](https://github.com/mishoo/UglifyJS2/blob/v2.x/lib/output.js) | | Lower level access to UglifyJS output. |
 | comments | boolean, RegExp, function(astNode, comment) -> boolean | Defaults to preserving comments containing `/*!`, `/**!`, `@preserve` or `@license`. | Comment related configuration. |
-| extractComments | boolean, RegExp, function (astNode, comment) -> boolean, object | false | Whether comments shall be extracted to a separate file, see below. |
+| extractComments | boolean, RegExp, function (astNode, comment) -> boolean, object | false | Whether comments shall be extracted to a separate file, (see [details](https://github.com/webpack/webpack/commit/71933e979e51c533b432658d5e37917f9e71595a), since webpack 2.3.0) |
 | sourceMap | boolean | false | Use SourceMaps to map error message locations to modules. This slows down the compilation. **Important!** `cheap` source map options don't work with the plugin! |
 | test | RegExp, Array<RegExp> | <code>/\.js($&#124;\?)/i</code> | Test to match files against. |
 | include | RegExp, Array<RegExp> | | Test only `include` files. |
 | exclude | RegExp, Array<RegExp> | | Files to `exclude` from testing. |
-| extractComments | boolean, RegExp, object | | Extract comments to separate file (see [details](https://github.com/webpack/webpack/commit/71933e979e51c533b432658d5e37917f9e71595a), since webpack 2.3.0) |
 | warningsFilter | function(source) -> boolean | | Allow to filter uglify warnings (since webpack 2.3.0) |
 
 <h2 align="center">Mangling</h2>