Fix fonts for assets

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/assets/stylesheets/base/fonts.scss

@@ -3,23 +3,23 @@
   font-family: 'Source Sans Pro';
   font-style: normal;
   font-weight: 300;
-  src: local('Source Sans Pro Light'), local('SourceSansPro-Light'), url('SourceSansPro-Light.ttf');
+  src: local('Source Sans Pro Light'), local('SourceSansPro-Light'), font-url('SourceSansPro-Light.ttf');
 }
 @font-face {
   font-family: 'Source Sans Pro';
   font-style: normal;
   font-weight: 400;
-  src: local('Source Sans Pro'), local('SourceSansPro-Regular'), url('SourceSansPro-Regular.ttf');
+  src: local('Source Sans Pro'), local('SourceSansPro-Regular'), font-url('SourceSansPro-Regular.ttf');
 }
 @font-face {
   font-family: 'Source Sans Pro';
   font-style: normal;
   font-weight: 600;
-  src: local('Source Sans Pro Semibold'), local('SourceSansPro-Semibold'), url('SourceSansPro-Semibold.ttf');
+  src: local('Source Sans Pro Semibold'), local('SourceSansPro-Semibold'), font-url('SourceSansPro-Semibold.ttf');
 }
 @font-face {
   font-family: 'Source Sans Pro';
   font-style: normal;
   font-weight: 700;
-  src: local('Source Sans Pro Bold'), local('SourceSansPro-Bold'), url('SourceSansPro-Bold.ttf');
+  src: local('Source Sans Pro Bold'), local('SourceSansPro-Bold'), font-url('SourceSansPro-Bold.ttf');
 }