Remove tryjruby and add blog

The Try Ruby site has not run JRuby for many years, and both
WebStart and applets are dead, so I remove all "tryjruby"
content.

To address jruby/jruby#8313 I add a Blog link to the top menu.

Fixes jruby/jruby#8313

Author: headius

_config.yml

@@ -18,7 +18,6 @@ release:
 urls:
   maven: https://repo1.maven.org/maven2/org/jruby
   s3: https://s3.amazonaws.com/jruby.org/downloads
-  tryjruby: https://s3.amazonaws.com/jruby.org/tryjruby
   bugs: https://github.com/jruby/jruby/issues
   jira: http://jira.codehaus.org/browse/JRUBY
   wiki: https://github.com/jruby/jruby/wiki

_includes/menu.html

@@ -5,12 +5,12 @@
         <li id="page_1" class="{% if page.title contains "Home" %}on{% endif %}">
           <a href="/">Home</a>
         </li>
-        <li id="page_16" class="{% if page.title contains "Try JRuby!" %}on{% endif %}">
-          <a href="/tryjruby">Try JRuby!</a>
-        </li>
         <li id="page_5" class="{% if page.title contains "News" %}on{% endif %}">
           <a href="/news">News</a>
         </li>
+        <li id="page_16" class="{% if page.title contains "Blog" %}on{% endif %}">
+        <a href="https://blog.jruby.org/">Blog</a>
+        </li>
         <li id="page_8" class="{% if page.title contains "Download" %}on{% endif %}">
           <a href="/download">Downloads</a>
         </li>

files/index.html

@@ -7,5 +7,4 @@ <h1>Files/</h1>
   <a href='/files/downloads/index.html'>downloads</a><br/>
   <a href='/files/prerelease/index.html'>prerelease</a><br/>
   <a href='/files/presentations/index.html'>presentations</a><br/>
-  <a href='/files/tryjruby/index.html'>tryjruby</a><br/>
 </p>