Merge pull request #2 from llonchj/from_crawler

From crawler
updated readme
removed deprecated scrapy settings.
added dependencies and classifiers, bump 0.2
use setuptools instead distutils to support install_requires.
added from_crawler() method to support latest scrapy versions.
allow to choose type of scheduling (queue, stack, priority queue) + tests.
example-project: added example queue class setting values.
example-project: added a note about FIFO/LIFO post processing of items.
fixed missing attribute typo.
updated readme and bumped version 0.3
fixed readme formatting
added installation notes.
Merge pull request #4 from llonchj/master

fix serialization