Ruby logger (#251)

* Add logger for ruby environment

* Update readme and example for ruby logger

* ruby-env: log load time for user code

environments/ruby/fission/context.rb

@@ -1,9 +1,14 @@
 # frozen_string_literal: true
 
 require_relative 'request'
+require 'forwardable'
 
 module Fission
   class Context
+    extend Forwardable
+
+    def_instance_delegator :request, :logger
+
     attr_reader :env
 
     def initialize(env)