use /assets/ to .css format

lib/bootstrap_beagle/version.rb

 module BootstrapBeagle
-  VERSION = "0.1.2"
+  VERSION = "0.1.3"
 end

vendor/assets/stylesheets/material-design-icons/css/material-design-iconic-font.css

@@ -5,7 +5,7 @@
 @font-face {
   font-family: 'Material Icons';
   /*src: url('../fonts/Material-Design-Iconic-Font.woff2?v=2.2.0') format('woff2'), url('../fonts/Material-Design-Iconic-Font.woff?v=2.2.0') format('woff'), url('../fonts/Material-Design-Iconic-Font.ttf?v=2.2.0') format('truetype');*/
-  src: url(asset_path('material-design-icons/fonts/Material-Design-Iconic-Font.woff2?v=2.2.0')) format('woff2'), url(asset_path('material-design-icons/fonts/Material-Design-Iconic-Font.woff?v=2.2.0')) format('woff'), url(asset_path('material-design-icons/fonts/Material-Design-Iconic-Font.ttf?v=2.2.0')) format('truetype');
+  src: url('/assets/material-design-icons/fonts/Material-Design-Iconic-Font.woff2?v=2.2.0') format('woff2'), url('/assets/material-design-icons/fonts/Material-Design-Iconic-Font.woff?v=2.2.0') format('woff'), url('/assets/material-design-icons/fonts/Material-Design-Iconic-Font.ttf?v=2.2.0') format('truetype');
   font-weight: normal;
   font-style: normal;
 }