fix a possible error in contracts post hook
command with multiple crawlers, fix check command
disable logging for scrapy check
also fetch alternate URLs from sitemaps, see #360
FilesPipeline which enalbes to download any files.
It has been extracted from ImagesPipelines.
ImagesPipeline is built on top of FilesPipeline and consist only with convert image and thumbnail generation logic.
Test reorganization and new tests for Files and Images Pipelines, PEP8 changes in MediaPipeline
default to multi crawler commands

compatibility for old single crawler process
deprecated command's `crawler` property
logs about settings only shown once
port all scrapy commands to new CrawlerProcess
typo
fix some missing logs with new crawlerprocess
fix log intermixing in scrapy shell command
remove redundant kwarg
remarks
typo
backwards compatibility: image_key
backwards compatibility: image_key & image_downloaded
after additional tests with actual s3: k.set_contents_from_string is working
don't start reactor if no crawler is scheduled
Merge pull request #370 from loucash/master

FilesPipeline extracted and separated from ImagesPipeline
Merge pull request #330 from alexcepoi/contracts_fix