added a bit more documentation on how to close the reactor when running scrapy from a script
remove wrong default httpcache
Merge pull request #326 from berendiwema/master

Include example of how to stop the reactor from script
removed request_received and added request_scheduled
Merge pull request #328 from nramirezuy/signals-request_scheduled

removed request_received and added request_scheduled
remove no deprecated request_scheduled signal

It will be replaced by more accurate scheduler signals (proposal will
come soon)
increase delay in test to avoid small time differences