Slightly more info on 404 page (Closes #4)

- Informing user why they are here
- Link to verify if they misspelled a link of theirs
- not much else informative you could put and not have the page look a mess, but
I'm open to suggestions

go/go/templates/404.html

@@ -10,6 +10,8 @@
   <div class="col-md-10 col-md-offset-1 text-center">
     <h1>404 Error - Page Not Found</h1>
 
+    <h3>The link you provided is invalid or may have been deleted.</h3>
+    <h3>If you are registered to use Go, you can verify your links <a href="{% url 'my_links' %}">here</a>.</h3>
     <img id="squirrels" src="/static/img/squirrels.png">
 
     <a href="/"><img src="/static/img/acorn.png" style="width:10vw;"></a>