Switch to side-by-side view

--- a/doc/Makefile
+++ b/doc/Makefile
@@ -4,8 +4,7 @@
 	asciidoc $<
 
 all: upmpdcli.html scmulti.html upmpdcli-or-mpdupnp.html \
-     release-0.8.html release-0.9.html \
-     release-0.11.html
+     releases.html
 
 clean:
 	rm -f *.html