updated fontawesome version (#174)

* updated fontawesome version

* Update CONTRIBUTORS.md

CONTRIBUTORS.md

@@ -35,3 +35,4 @@
 - [Thomas Vochten](https://github.com/thomasvochten)
 - [Caspar Krieger](https://www.asparck.com)
 - [D_DAndrew](https://d-dandrew.github.io)
+- [Wataru Mizukami](https://github.com/tarumzu)

layouts/_default/baseof.html

@@ -22,7 +22,7 @@
     {{ end }}
 
     <link href="https://fonts.googleapis.com/css?family=Lato:400,700%7CMerriweather:300,700%7CSource+Code+Pro:400,700" rel="stylesheet">
-    <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.3.1/css/all.css" integrity="sha384-mzrmE5qonljUremFsqc01SB46JvROS7bZs3IO2EmfFsd15uHvIt+Y8vEf7N7fWAU" crossorigin="anonymous" />
+    <link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.8.1/css/all.css" integrity="sha384-50oBUHEmvpQ+1lW4y57PTFmhCaXp0ML5d60M1M7uH2+nqUivzIebhndOJK28anvf" crossorigin="anonymous" />
     <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/normalize/8.0.0/normalize.min.css" integrity="sha256-oSrCnRYXvHG31SBifqP2PM1uje7SJUyX0nTwO2RJV54=" crossorigin="anonymous" />
 
     {{ if .Site.IsServer }}