Updated documentation on how to install the Jekyll version that comes with github-pages.

Author: hategan

README-dev.md

@@ -48,8 +48,8 @@ Make sure that `build.sh` is called from the main directory. The output will
 be in `web-build`.
 
 3. Render the web site and themed documentation, which can be done using Jekyll.
-To install Jekyll, follow these
-[instructions](https://jekyllrb.com/docs/installation/). Then run
+To install Jekyll, follow the instructions in step 2 of 
+[web/README.md](web/README.md). You only need to do this once. Then run
 
     ```
     web/serve.sh

web/README.md

@@ -22,7 +22,18 @@ PSI/J repository.
     $ sudo pip install -r requirements-docs.txt
     ```
 
- 2. Install Jekyll (see [Jekyll Installation](https://jekyllrb.com/docs/installation/) - also a one-time operation).
+ 2. Install Jekyll prerequisites by following the instructions for your
+ operating system found in the 
+ [Jekyll installation instructions](https://jekyllrb.com/docs/installation/).
+ You should skip installing Jekyll itself, since it will be installed by 
+ *bundler*. Then run
+    ```bash
+    $ cd web
+    $ bundle update
+    $ cd ..
+    ```
+ to install the version of Jekyll used by github-pages. This is a one-time
+ operation. For subsequent builds, you can skip directly to step 3.
 
  3. Run the build script, which will build the documentation, process
  files in the `web` directory, and generate the output in `web-build`: