Update website to highlight beta 0.13.0 release

Also mention the Slack channel, and remove link to no-longer-supported
0.11.2 documentation.

Author: deanberris

index.html

@@ -64,6 +64,24 @@ <h1>Overview</h1>
                         <div class="page-header">
                             <h1>Download</h1>
                         </div>
+                        <p>The current <strong>beta release</strong> of the library is available in three formats, please pick one of the three:</p>
+                        <div class="row">
+                            <div class="col-md-4">
+                                <a href="http://downloads.cpp-netlib.org/0.13.0/cpp-netlib-0.13.0-rc0.zip" class="btn btn-primary btn-lg btn-block">0.13.0-rc0 (zip)</a>
+                                <br>
+                                <small class="text-muted cpp-netlib-hash">md5: 73a25a7d37a38762465f1e37c52b02e6</small>
+                            </div>
+                            <div class="col-md-4">
+                                <a href="http://downloads.cpp-netlib.org/0.13.0/cpp-netlib-0.13.0-rc0.tar.gz" class="btn btn-primary btn-lg btn-block">0.13.0-rc0 (tar.gz)</a>
+                                <br>
+                                <small class="text-muted cpp-netlib-hash">md5: 484949520b741c3cd5cb2a25366180d2</small>
+                            </div>
+                            <div class="col-md-4">
+                                <a href="http://downloads.cpp-netlib.org/0.13.0/cpp-netlib-0.13.0-rc0.tar.bz2" class="btn btn-primary btn-lg btn-block">0.13.0-rc0 (tar.bz2)</a>
+                                <br>
+                                <small class="text-muted cpp-netlib-hash">md5: e1a6f78df1dd1a45c3fd26647baf7b9e</small>
+                            </div>
+                        </div>
                         <p>The current <strong>stable release</strong> of the library is available in three formats, please pick one of the three:</p>
                         <div class="row">
                             <div class="col-md-4">
@@ -92,9 +110,6 @@ <h1>Documentation</h1>
                             <div class="col-md-4">
                                 <a href="0.12.0/index.html" class="btn btn-primary btn-lg btn-block">0.12.0 (stable)</a>
                             </div>
-                            <div class="col-md-4">
-                                <a href="0.11.2/index.html" class="btn btn-warning btn-lg btn-block">0.11.2 (previous stable)</a>
-                            </div>
                             <div class="col-md-4">
                                 <a href="0.10.1/index.html" class="btn btn-danger btn-lg btn-block">0.10.1 (previous unsupported)</a>
                             </div>
@@ -104,7 +119,8 @@ <h1>Documentation</h1>
                         <div class="page-header">
                             <h1>Support</h1>
                         </div>
-                        <p>We offer two avenues of support for user issues, depending on what kind of issues you're encountering.</p>
+                        <h2>Join us on Slack!</h2>
+                        <p><a href="http://slack.cpp-netlib.org/" class="btn btn-block">cpp-netlib Slack</a></p>
                         <h2>Reporting Bugs</h2>
                         <p>If you're using the library and would like to report issues with the library, please file your bug reports and support requests in the official issue tracker.</p>
                         <p><a href="https://github.com/cpp-netlib/cpp-netlib/issues" class="btn btn-danger btn-large">File Bugs</a></p>