Add Requires on mallard-rng for schemas

The dependency will be added in a future version of yelp-tools, but for
now it makes yelp-check work better offline.

https://bugzilla.gnome.org/show_bug.cgi?id=765215#c2

yelp-tools.spec

@@ -1,6 +1,6 @@
 Name:          yelp-tools
 Version:       3.18.0
-Release:       2%{?dist}
+Release:       3%{?dist}
 Summary:       Create, manage, and publish documentation for Yelp
 
 Group:         Applications/Publishing
@@ -15,6 +15,7 @@ BuildRequires: libxslt
 
 Requires: /usr/bin/itstool
 Requires: /usr/bin/xmllint
+Requires: mallard-rng
 Requires: yelp-xsl
 
 %description
@@ -43,6 +44,9 @@ make %{?_smp_mflags}
 %{_datadir}/aclocal/yelp.m4
 
 %changelog
+* Tue Apr 26 2016 David King <amigadave@amigadave.com> - 3.18.0-3
+- Add Requires on mallard-rng for schemas
+
 * Fri Feb 05 2016 Fedora Release Engineering <releng@fedoraproject.org> - 3.18.0-2
 - Rebuilt for https://fedoraproject.org/wiki/Fedora_24_Mass_Rebuild