Update mini-racer for Mac OS Sierra (#338)

Author: justin808

Gemfile.lock

@@ -117,7 +117,7 @@ GEM
     json (1.8.3)
     launchy (2.4.3)
       addressable (~> 2.3)
-    libv8 (5.0.71.48.3)
+    libv8 (5.3.332.38.1)
     listen (3.1.5)
       rb-fsevent (~> 0.9, >= 0.9.4)
       rb-inotify (~> 0.9, >= 0.9.7)
@@ -131,8 +131,8 @@ GEM
       mime-types-data (~> 3.2015)
     mime-types-data (3.2016.0521)
     mini_portile2 (2.1.0)
-    mini_racer (0.1.4)
-      libv8 (~> 5.0, < 5.1.11)
+    mini_racer (0.1.7)
+      libv8 (~> 5.3)
     minitest (5.9.0)
     multi_json (1.12.1)
     nio4r (1.2.1)
@@ -355,4 +355,4 @@ RUBY VERSION
    ruby 2.3.1p112
 
 BUNDLED WITH
-   1.12.5
+   1.13.6