fix link to online installation instructions
Raise error when settings module is missing.

Previously, it failed silently if an ImportError was caught when trying
to import the scrapy settings module. This not only happened when the
scrapy settings module itself was missing, but also when it tried to
import a missing module, which made the whole thing a bad idea.

A side effect of this change (not required, but for simplification) is
that we no longer support the default "scrapy_settings" name for the
scrapy settings module, but this was never used afaik.
response.meta exposes resquest.meta for binded responses
fix for request's errback, allows to get failed requests correctly
Merge pull request #179 from artem-dev/errback_fix

This fixes the case where failure.request wasn't available when the failure was generated in a spider middleware (for example, the HttpError middleware).
more cases where response.meta is prefered
notify #scrapy room of travis build results
fix test-scrapyd.sh after changes made to website
added response_received_count to scrapy stats
don't reset scrapy stats when spider is opened
Track number of log messages via Scrapy stats

Log messages count are grouped per LEVEL like:

    'log_count/DEBUG': 8,
    'log_count/ERROR': 1,
    'log_count/INFO': 4,

This required passing the Crawler object to scrapy logging facility, so
the scrapy.log module underwent a few changes which should be backwards
compatible (or as backwards compatible as they could be).
updated release notes with new stats recently added
fixed doc reference to topics-contracts
removed scrapy.log.started attribute, and avoid checking if log has already been started (since it should be called once anyway)
httpcompression middleware improvement
minor message update: spider stats -> Scrapy stats
added deprecation warning when importing scrapy.conf module
simplified backwards compatibility of scrapy.conf
better description for scrapy check command
updated scrapy_bash_completion