Merge pull request #5096 from MikeMcQuaid/descriptions-cache

Library/Homebrew/cache_store.rb

Library/Homebrew/cleanup.rb

Library/Homebrew/cmd/desc.rb

Library/Homebrew/cmd/update-report.rb

Library/Homebrew/description_cache_store.rb

Library/Homebrew/descriptions.rb

Library/Homebrew/keg.rb

Library/Homebrew/linkage_cache_store.rb

Library/Homebrew/linkage_checker.rb

Library/Homebrew/search.rb

Library/Homebrew/tap.rb

Library/Homebrew/test/cmd/desc_spec.rb

Library/Homebrew/test/cmd/search_spec.rb

Library/Homebrew/test/description_cache_store_spec.rb

Library/Homebrew/test/linkage_cache_store_spec.rb