corrected paths to node_modules folder used by benchmark, updated contributing docs for benchmark

CONTRIBUTING.md

@@ -1,8 +1,16 @@
 ### If you commit changes:
 
 1. Make sure all tests pass.
-2. Run `./benchmark/benchmark.js`, make sure that performance not degraded.
-3. DON'T include auto-generated browser files to commit.
+2. Install dependencies for benchmark:
+
+```
+npm i benchmark
+npm i commonmark
+npm i marked
+```
+
+3. Run `./benchmark/benchmark.js`, make sure that performance not degraded.
+4. DON'T include auto-generated browser files to commit.
 
 ### Other things:
 

benchmark/implementations/commonmark-reference/index.js

@@ -1,6 +1,6 @@
 'use strict';
 
-var commonmark = require('../../extra/lib/node_modules/commonmark');
+var commonmark = require('../../../node_modules/commonmark');
 var parser = new commonmark.Parser();
 var renderer = new commonmark.HtmlRenderer();
 

benchmark/implementations/markdown-it-2.2.1-commonmark/index.js

@@ -1,6 +1,6 @@
 'use strict';
 
-var md = require('../../extra/lib/node_modules/markdown-it')('commonmark');
+var md = require('../../../node_modules/markdown-it')('commonmark');
 
 exports.run = function (data) {
   return md.render(data);

benchmark/implementations/marked/index.js

@@ -1,6 +1,6 @@
 'use strict';
 
-var marked = require('../../extra/lib/node_modules/marked');
+var marked = require('../../../node_modules/marked');
 
 exports.run = function (data) {
   return marked(data);