Gitignore contributors data (#1429)

* Gitignore contributor data

It's generated from the rubygems/rubygems repo so it's not necessary to
keep it source controlled here.

* Suggest `rake build` rather than `rake man` in README

`rake build` is necessary to generate contributor data file, which is
necessary to render the contributors page.

* Rename `contributors:update` task to `contributors`

Since we no longer keep the yaml file in source control, I think the
`update` part has lost most of its meaning.

.gitignore

@@ -28,6 +28,9 @@ source/changelog.html.md
 source/conduct.html.md
 source/doc
 
+# contributor data generated from the bundler repo
+data/contributors.yml
+
 # man pages built from the bundler repo
 /source/v*/man/
 

README.md

@@ -25,9 +25,9 @@ Or you can prepare a development environment on Gitpod cloud from the below link
 
 ## Basic Middleman Commands
 
-Fetch latest documentation from bundler repo (should be done before running local development web server):
+Fetch latest documentation and contributor information from bundler repo (should be done before running local development web server):
 
-    bundle exec rake man
+    bundle exec rake build
 
 Run a local development web server:
 

Rakefile

@@ -1,7 +1,7 @@
 Dir.glob("lib/tasks/**/*.rake").each { |r| load r }
 
 desc "Build the static site"
-task build: ["contributors:update", :repo_pages, :man] do
+task build: [:contributors, :repo_pages, :man] do
   sh "middleman build --clean --verbose"
 end