Change the tagline

Apparently until I stop bullshitting ppl in the tagline I won't get
my hands on to finishing this feature (been 6 months since it was on a
branch).

doc/www-data.in/index

@@ -3,7 +3,7 @@
 {% text blurb en %}
 
 # Tarantool
-## A transactional NoSQL database
+## An in-memory NoSQL database
 ###[Overview](intro.html)    [Documentation](tarantool_user_guide.html)    [Download](download.html)    [Support](support.html)
 
 {% text blurb ru %}