Add magic token to hide commands from man page

Closes #402.

Library/Homebrew/cmd/help.rb

@@ -91,8 +91,9 @@ module Homebrew
         line.slice(2..-1).
           sub(/^  \* /, "#{Tty.highlight}brew#{Tty.reset} ").
           gsub(/`(.*?)`/, "#{Tty.highlight}\\1#{Tty.reset}").
-          gsub(/<(.*?)>/, "#{Tty.em}\\1#{Tty.reset}")
-      end.join
+          gsub(/<(.*?)>/, "#{Tty.em}\\1#{Tty.reset}").
+          gsub("@hide_from_man_page", "")
+      end.join.strip
     end
   end
 end

Library/Homebrew/cmd/man.rb

@@ -51,7 +51,7 @@ module Homebrew
           map { |line| line.slice(2..-1) }.
           join
       }.
-      reject { |s| s.strip.empty? }
+      reject { |s| s.strip.empty? || s.include?("@hide_from_man_page") }
 
     variables[:maintainers] = (HOMEBREW_REPOSITORY/"README.md").
       read[/Homebrew's current maintainers are (.*)\./, 1].

Library/Homebrew/cmd/tests.rb

+#: @hide_from_man_page
 #:  * `tests` [`-v`] [`--coverage`] [`--generic`] [`--no-compat`] [`--only=`<test_script/test_method>] [`--seed` <seed>] [`--trace`]:
 #:    Run Homebrew's unit and integration tests.