Explicitly check if an object is a class is pydispatch.

* This is to fix a disagreement in between CPython and PyPy.
* https://gist.github.com/4220533
PEP8 on pydispatch/robustapply.py
added ftp handler
allow passing arguments to tox

e.g. "tox -- scrapy.tests.test_contrib_loader" runs test_contrib_loader for Python 2.6 and 2.7
use tox deps instead of "manual" pip install; add lucid and precise environments to tox.ini
add django to test requirements and fix test_djangoitem for modern django versions
make tox test running more consistent with bin/runtests.sh script
reuse runtests.sh and runtests.bat scripts in tox.ini
allow passing arguments to runtests script via tox
tiny FormRequest doc fix
use lxml parser with recover option to parse invalid sitemaps. closes #347

thanks chrissboo for reporting the issue and proposing a fix.
Merge branch 'gh-347'. thanks @chrisboo
Merge pull request #329 from kalessin/ftphandler

added ftp handler
Twisted pre 10.2 (lucid) can not setup the required ftp server for tests
Merge pull request #341 from kmike/test-running

Improved tox test running & fixed django tests
Updated documentation of spider arguments to include required super call.
Fixed ordering of super argument call.
take in count response latencies when testing download delays
Merge pull request #350 from dellis23/master

This pull request fixes #349
Merge pull request #205 from joehillen/master

PyPy support