Simplify the install instructions
Simplify the install instructions

* Uses `sudo sed`, as Xcode can't edit root owned files
* Curl directly into /Library/LaunchDaemons
es/agent,joelmoss/agent,Jasperswaagman/agent,es/agent,buildkite/agent,tommeier/agent,es/agent,Shopify/agent,grosskur/agent,joelmoss/agent,Jasperswaagman/agent,joelmoss/agent,buildkite/agent,Shopify/agent,grosskur/agent,buildkite/agent,Shopify/agent,tommeier/agent,tommeier/agent,grosskur/agent,Jasperswaagman/agent