Add the exact versions to the vulcanize.md install command.

docs/vulcanize.md

Index: docs/vulcanize.md
diff --git a/docs/vulcanize.md b/docs/vulcanize.md
index b29051d89afbc22d6c0fbd79ea1d1c4b0b54aa2a..4e0daf2a7b7becda5bc397f50406bad08d23f22f 100644
--- a/docs/vulcanize.md
+++ b/docs/vulcanize.md
@@ -28,9 +28,8 @@ $ npm config set -g prefix "$HOME/node_modules"
 
 Then install the required modules:
 
-```bash
-$ npm install -g crisper vulcanize uglifyjs polymer-css-build
-```
+    bash $ npm install -g crisper@2.0.1 vulcanize@1.14.8 \
+           uglifyjs@2.4.10 polymer-css-build@0.0.6

[tsergeant, 2016/11/24 03:30:29]

I don't recognize this syntax? The regular github-flavoured markdown way to do
this would be

```bash
$ npm install -g crisper@2.0.1 vulcanize@1.14.8 uglifyjs@2.4.10 \
    polymer-css-build@0.0.6
```

(see:
https://gerrit.googlesource.com/gitiles/+/master/Documentation/markdown.md#Co...)

[calamity, 2016/11/24 06:03:04]

Done.

 
 Ultimately, all that is required to run this script is that the node binaries
 listed above are on your $PATH.