Update gems with potential security vulnerabilities

Author: cybette

Gemfile.lock

@@ -97,7 +97,7 @@ GEM
     minitest (5.9.0)
     multipart-post (2.0.0)
     net-dns (0.8.0)
-    nokogiri (1.6.8)
+    nokogiri (1.8.2)
       mini_portile2 (~> 2.1.0)
       pkg-config (~> 1.1.7)
     octokit (4.3.0)
@@ -124,7 +124,7 @@ GEM
       ethon (>= 0.8.0)
     tzinfo (1.2.2)
       thread_safe (~> 0.1)
-    yajl-ruby (1.2.1)
+    yajl-ruby (1.3.1)
 
 PLATFORMS
   ruby