Make Rake a runtime dep

just-the-docs.gemspec

@@ -2,7 +2,7 @@
 
 Gem::Specification.new do |spec|
   spec.name          = "just-the-docs"
-  spec.version       = "0.1.3"
+  spec.version       = "0.1.4"
   spec.authors       = ["Patrick Marsceill"]
   spec.email         = ["patrick.marsceill@gmail.com"]
 
@@ -14,7 +14,7 @@ Gem::Specification.new do |spec|
   spec.executables   << 'just-the-docs'
 
   spec.add_runtime_dependency "jekyll", "~> 3.3"
+  spec.add_runtime_dependency "rake", "~> 10.0"
 
   spec.add_development_dependency "bundler", "~> 1.12"
-  spec.add_development_dependency "rake", "~> 10.0"
 end