Add alt link to profile headshots

_includes/person-card.html

 <div class="col-sm-4 card text-xs-center">
   <a href="{{ person.url }}">
-    <img class="img-circle" src="{{ person.image | prepend: site.baseurl }}" />
+    <img class="img-circle" src="{{ person.image | prepend: site.baseurl }}" alt="Photo of {{ person.firstname }} {{ person.lastname }}" />
     <h4 class="card-title">{{ person.firstname }} {{ person.lastname }}</h4>
   </a>
   <h6 class="card-subtitle text-muted">{{ person.position }}</h6>

_layouts/person.html

@@ -10,7 +10,7 @@ menu: false
 <div class="row">
   <div class="col-sm-4">
     <div class="card">
-      <img class="img-circle center-block" style="width: 50%" src="{{ page.image | prepend: site.baseurl }}" />
+      <img class="img-circle center-block" style="width: 50%" src="{{ page.image | prepend: site.baseurl }}" alt="Photo of {{ page.firstname }} {{ page.lastname }}" />
       <div class="list-group list-group-flush">
         <a class="list-group-item" href="{{ page.webpage }}"><i class="fa fa-fw fa-globe"></i>&nbsp; Webpage</a>
         <a class="list-group-item" href="mailto:{{ page.email }}"><i class="fa fa-fw fa-envelope-o"></i>&nbsp; {{ page.email }}</a>