Handle cases when inspect.stack() fails
testing PIL dependency is removed because there is a new mitmproxy version
Fix wrong checks on subclassing of deprecated classes. closes #581
Merge pull request #584 from dangra/581-deprecated-subclass-fix

Fix wrong checks on subclassing of deprecated classes
Merge pull request #585 from kmike/mitmproxy-reqs-cleanup

[MRG] testing PIL dependency is removed because there is a new mitmproxy version
test inspect.stack failure
Merge pull request #582 from kmike/inspect-workaround

[WIP] Handle cases when inspect.stack() fails
localhost666 can resolve under certain circumstances

localhost666 is resolvable if the host running the tests contains a
"search mydomain.com" in /etc/resolv.conf and a wildcard dns entry
exists for *.mydomain.com
Add 0.22.1 release notes
Correct typos
downloaderMW doc typo (spiderMW doc copy remnant)
Merge pull request #590 from Digenis/master

downloaderMW doc typo (spiderMW doc copy remnant)
add SEP-021 (Add-ons) - work in progress
fix a reference to unexistent engine.slots. closes #593
Merge pull request #594 from dangra/593-engineslots

fix a reference to unexistent engine.slots.
Add 0.22.2 release notes
DOC Use pipelines module name instead of pipieline following default project files.
Merge pull request #596 from darkrho/doc-pipeline

DOC Use pipelines module name instead of pipieline following default project files.
remove references to deprecated scrapy-developers list
TST Improved twisted installation in tox.ini for Python 3.3

Install twisted trunk because released twisted doesn't install properly,
see https://twistedmatrix.com/trac/ticket/6539.

Also, test-requirements are removed for 3.3 because mitmproxy doesn't
install in Python 3.3, and mock is in Python 3.3 standard library.

Note that trial scrapy is not doing what is expected because twisted doesn't
have trial runner for 3.3 yet, so this command will most likely call "trial"
outside tox virtualenv and will use incorrect interpreter.