Added build instructions link to download page.

download.html

@@ -51,7 +51,9 @@
 
           <p>Briar for Android is currently in private beta and will be available for download soon. If you'd like to be informed when the app is available, please <a href="https://lists.sourceforge.net/lists/listinfo/briar-announce">join the announcement mailing list</a>.</p>
 
-          <p>If you're a developer, you can <a href="https://code.briarproject.org/akwizgran/briar">check out the source code</a> and <a href="https://lists.sourceforge.net/lists/listinfo/briar-devel">join the development mailing list</a>.</p>
+          <p>If you're interested in getting involved or following the progress of the project, please <a href="https://lists.sourceforge.net/lists/listinfo/briar-devel">join the development mailing list</a> or email <a href="mailto:contact@briarproject.org">contact@briarproject.org</a> [<a href="keys/contact.asc">PGP key</a>].</p>
+
+          <p>All our software is open source - you can <a href="https://code.briarproject.org/akwizgran/briar/tree/master">browse the source code</a> or <a href="building.html">build the app from source</a>.
 
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