Ignore None's values when using the ItemLoader.
Unused re import and PEP8 minor edits.
Expose current crawler in the scrapy shell.
PEP8 minor edits.
Updated shell docs with the crawler reference and fixed the actual shell output.

Also updated the shell example with a reproducible code example.
Updated the tutorial crawl output with latest output.
Merge pull request #556 from darkrho/item-loader-nones

Make `ItemLoader` ignore `None` values from processors.
replace unencodeable codepoints with html entities. fixes #562 and #285
Merge pull request #557 from darkrho/expose-crawler-in-shell

Expose current crawler in the scrapy shell.
Merge pull request #565 from dangra/562-sgmlinkextractor

replace unencodeable codepoints with html entities