Fixed case for Fn-headers according to the container contract

Added Fn-Fdk-Version header to response

Author: Gaurav Saini

lib/fdk/context.rb

@@ -51,6 +51,7 @@ def each(&block)
   # Represents outbound HTTP headers
   class OutHeaders < InHeaders
     def initialize(headers, key_in_fn)
+      headers["Fn-Fdk-Version"] = ["fdk-ruby/#{FDK::VERSION}"]
       super(headers, key_in_fn)
     end
 

tests/test_fdk.rb

@@ -66,6 +66,7 @@ def test_handle_simple_request()
       assert_equal 200, resp.code.to_i
       assert_equal "\"hello world\"", resp.body
       assert_equal "application/json", resp["content-type"]
+      assert_equal "fdk-ruby/#{FDK::VERSION}", resp["Fn-Fdk-Version"]
     }
   end