doc: fixed rst title
made scrapy/item.py pep8 compliant
added 502 to RETRY_HTTP_CODES
arg_to_iter: treat items the same way as dicts (ie. non iterables). fixes #248
arg_to_iter: replaced double call to isinstance with a single one. refs #248
remove debugging code
Log overriden Scrapy settings when Scrapy starts.

This is useful for debugging, to quickly find out which settings where
used for a specific spider run. dict settings are omitted for brevity.
DEBUG level is used for consistency with "Enabled
extensions/middlewares" lines (which share a similar purpose).
doc: fix typo in spider middleware
fetch command should catch IgnoreRequest exception
Merge pull request #257 from stav/cleanups

doc: fix typo in spider middleware
docs/contributing: added note explaining what Scrapy contrib is
Merge branch 'shell' of git://github.com/stav/scrapy into stav-shell
pluggable sub-commands for scrapy comand-line
added documentation (experimental feature)
allow spider allowed_domains to be set/tuple, #259
Some changes to scrapy deploy command:

- use branch names when constructing HG/GIT versions
- added -d flag for debugging (keeps build directory)
- improved command output (redirected setup.py stderr)
added SEP-019 (per-spider settings) - first draft
sep-019: minor tide up
sep-019: fix typos
sep-019: other minor fixes