Add 'bundle exec jekyll serve' instruction to README.md

Author: dangerworm

Gemfile

@@ -6,3 +6,5 @@ source "https://rubygems.org"
 git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
 
 gem 'github-pages', group: :jekyll_plugins
+
+gem 'wdm', '>= 0.1.0' if Gem.win_platform?

README.md

@@ -57,15 +57,15 @@ Open a command line in the root directory of the repository.
 
 If this is the first time you have built the site, make sure you have run `bundle pack` before attempting to build the site using jekyll.
 
-Otherwise, run `bundle exec jekyll build` to build the site, this will produce a `_site` folder with the required content.
+Next, run `bundle exec jekyll build` to build the site. This will produce a `_site` folder with the required content.
 
 >:Warning: do not edit anything in the site folder as it will not be comitted and is overwritten everytime you build the site.
 
-To rebuild the site after a file change append `--watch` to the end of the command. 
+Once you have a `_site` folder, open the `index.html` file inside to view the site.
 
-e.g. `bundle exec jekyll build --watch`
+You will normally need to rebuild the site every time you save a change to a file. To rebuild the site automatically after each update append `--watch` to the end of the command, i.e. `bundle exec jekyll build --watch`
 
-Once you have a `_site` folder open the `index.html` file inside to view the site.
+>:Warning: The website uses extensionless links, meaning we don't need to include the '.html' extension on web pages and in anchor (<a>) links. In order that these links work while you view the site locally, open a new command-line window, navigate to the folder containing the website's source code, and run `bundle exec jekyll serve`. Leave that window running while you make your changes.
 
 ## Includes