Moving require so that client only gets loaded if the task requires it.

tasks/wiki.rake

@@ -1,4 +1,3 @@
-require 'google/api_client'
 require 'rake'
 require 'rake/clean'
 
@@ -18,6 +17,7 @@ the following Google APIs.
 
 WIKI
     preferred_apis = {}
+    require 'google/api_client'
     client = Google::APIClient.new
     for api in client.discovered_apis
       if !preferred_apis.has_key?(api.name)