Downgrade execjs gem due to error in new version

See GitHub issue here: rails/execjs#99

Author: bradonomics

Gemfile

@@ -9,5 +9,7 @@ group :jekyll_plugins do
   gem 'jekyll-autoprefixer'
 end
 
+gem 'execjs', '2.7'
+
 # Add webrick gem for local development
 gem 'webrick'

Gemfile.lock

@@ -11,7 +11,7 @@ GEM
       eventmachine (>= 0.12.9)
       http_parser.rb (~> 0.6.0)
     eventmachine (1.2.7)
-    execjs (2.8.0)
+    execjs (2.7.0)
     ffi (1.15.0)
     forwardable-extended (2.6.0)
     http_parser.rb (0.6.0)
@@ -73,6 +73,7 @@ PLATFORMS
   x86_64-linux
 
 DEPENDENCIES
+  execjs (= 2.7)
   jekyll
   jekyll-autoprefixer
   jekyll-feed