diff --git a/Gemfile b/Gemfile
index fb9733d..f52d7ba 100644
--- a/Gemfile
+++ b/Gemfile
@@ -4,6 +4,7 @@ source "https://rubygems.org"
 # Documentation
 gem "rdoc"
 gem "redcarpet"
+gem "thor"
 gem "yard"
 gem "yard-ghpages"
 
diff --git a/Gemfile.lock b/Gemfile.lock
index 8830853..bd564d0 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -18,6 +18,7 @@ GEM
       ruby-progressbar (~> 1.7)
       unicode-display_width (~> 1.0, >= 1.0.1)
     ruby-progressbar (1.8.1)
+    thor (0.20.0)
     unicode-display_width (1.2.1)
     yard (0.9.9)
     yard-ghpages (0.0.2)
@@ -32,8 +33,9 @@ DEPENDENCIES
   rdoc
   redcarpet
   rubocop
+  thor
   yard
   yard-ghpages
 
 BUNDLED WITH
-   1.13.7
+   1.14.6