remove duplicated link extractors link

Check http://doc.scrapy.org/en/latest/topics/link-extractors.html - two menu items are highlighted at the left.
allow running individual tests via tox, e.g. «tox -e trunk -- scrapy.tests.test_spider»
Fixes #368: Support functools.partial in scrapy.utils.python.get_func_args()
Merge pull request #503 from kmike/better-tox-ini

[MRG] allow running individual tests via tox
minor fixes to scrapy shell docs

* better IPython links;
* MDC link instead of w3schools;
* small formatting fixes;
* show quoted URL in example
do not return applied arguments on partial functions
test loader processors using partial functions
Merge pull request #505 from kmike/scrapy-shell-docs

[MRG] minor fixes to scrapy shell docs
utility for showing a warning when a class is subclassed
Rename BaseSpider to Spider. See GH-495.
improved deprecation code; add some test
Rename warn_when_subclassed to deprecated_base_class; add some magic for issubclass and isinstance checks to work if subclasses of non-deprecated class are checked against deprecated class.
Merge pull request #506 from dangra/ahbeng-368-get-func-args-partial-support

get func args partial support - based on #504
simplify deprecation code (@dangra’s idea)
allow caller to customize clsdict
support overriding url in FormRequest.from_response
Hold the deprecated class reference in the metaclass
warn when the deprecated class is instanciated
Merge pull request #507 from dangra/fromresponse_override_url

[MRG] support overriding url in FormRequest.from_response
Merge pull request #510 from dangra/kmike-reanme-base-spider

Rename BaseSpider to Spider. Fixes #495, fixes #501.