added page last modified

Gemfile

@@ -1,3 +1,4 @@
 source "https://rubygems.org"
 
-gem 'github-pages'
+gem 'github-pages'
+gem 'jekyll-last-modified-at'

Gemfile.lock

@@ -97,6 +97,9 @@ GEM
     jekyll-github-metadata (2.3.1)
       jekyll (~> 3.1)
       octokit (~> 4.0, != 4.4.0)
+    jekyll-last-modified-at (1.0.1)
+      jekyll (~> 3.3)
+      posix-spawn (~> 0.3.9)
     jekyll-mentions (1.2.0)
       activesupport (~> 4.0)
       html-pipeline (~> 2.3)
@@ -170,6 +173,7 @@ GEM
       sawyer (~> 0.8.0, >= 0.5.3)
     pathutil (0.14.0)
       forwardable-extended (~> 2.6)
+    posix-spawn (0.3.11)
     public_suffix (2.0.5)
     rb-fsevent (0.9.8)
     rb-inotify (0.9.10)
@@ -194,6 +198,7 @@ PLATFORMS
 
 DEPENDENCIES
   github-pages
+  jekyll-last-modified-at
 
 BUNDLED WITH
    1.15.1

_config.yml

@@ -16,3 +16,5 @@ sass:
 collections:
     examples:
         output: true
+gems:
+  - jekyll-last-modified-at

_layouts/example.html

@@ -4,6 +4,7 @@
       <header class="example-header">
         <h1>{{page.title}}</h1>
         <p style="max-width: 40em; ">{{page.overview}}</p>
+
       </header>
 
       <article>
@@ -25,6 +26,12 @@ <h2>{{ principle.principle }}</h2>
       <aside>
 
 
+            <p class="source">
+              Last modified:
+            </p>
+            <p>
+              {{ page.last_modified_at | date: '%d %B %Y' }}
+            </p>
             {% if page.author %}
               <p class="source">
                 Author:

_layouts/home.html

@@ -54,6 +54,7 @@ <h2 class="intro">Who use them?</h2>
               </div>
             <h2><a href="{{example.url}}">{{example.title}}</a></h2>
             <p>{{example.author}}</p>
+            <p>{{ page.last_modified_at | date: '%d %B %Y' }}</p>
             <!-- <ol class="cards">
             {% for principles in example.principles %}
               <li><a href="{{example.url}}/#{{principles.principle | slugify}}">{{principles.principle}}</a></li>