Use a slightly heavier Raleway for headings (fixes #493)

gui/raleway.css

@@ -1,12 +1,6 @@
 @font-face {
   font-family: 'Raleway';
   font-style: normal;
-  font-weight: 400;
-  src: local('Raleway'), url(raleway-400.ttf) format('truetype');
-}
-@font-face {
-  font-family: 'Raleway';
-  font-style: normal;
-  font-weight: 700;
-  src: local('Raleway Bold'), local('Raleway-Bold'), url(raleway-700.ttf) format('truetype');
+  font-weight: 500;
+  src: local('Raleway'), url(raleway-500.ttf) format('truetype');
 }