Define initial Listener API.

lib/listener.rb

@@ -1,2 +1,17 @@
 module Listener
+
+  # Listen to file system modifications.
+  #
+  # @param [String, Pathname] dir the directory to watch
+  # @param [Hash] options the listen options
+  # @option options [String] glob the file filter pattern
+  # @yield [modified, added, removed] the changed files
+  # @yieldparam [Array<String>] modified the list of modified files
+  # @yieldparam [Array<String>] added the list of added files
+  # @yieldparam [Array<String>] removed the list of removed files
+  # @return [Watcher] the file watcher
+  #
+  def self.listen(dir, options, &block)
+  end
+
 end