Update YARD doc

Author: duffn

CONTRIBUTING.md

@@ -58,7 +58,7 @@ Make sure that `bundle exec rake` completes without errors.
 
 Document any external behavior in the [README](README.md).
 
-You should also document code as necessary, using current code as examples. This project uses [YARD](https://yardoc.org/). You can run and preview the docs locally by running `bundle exec yard server --reload` and view the docs at http://localhost:8808.
+You should also document code as necessary, using current code as examples. This project uses [YARD](https://yardoc.org/). You can run and preview the docs locally by [installing `yard`](https://yardoc.org/), running `yard server --reload` and view the docs at http://localhost:8808.
 
 #### Update Changelog
 

Gemfile

@@ -23,7 +23,6 @@ group :development do
   gem 'guard'
   gem 'guard-rspec'
   gem 'guard-rubocop'
-  gem 'yard'
 end
 
 group :test do