PY3 enable tests for scrapy parse command

scrapy parse command is already ported

[MRG+1] Py3: port test crawl

py3: pass CrawlTestCase.test_referer_header, fixing Echo resource in mockserver and json decoding in test

PY3 fixed scrapy bench command

[MRG+1] py3 fix HttpProxy and Retry Middlewares

[MRG+1] change os.mknod() for open()

Fix version number to appear new feature

[MRG+1] Py3: port commands fetch and shell

[MRG+1] Py3: port test_engine

[MRG+1] Implement FormRequest.from_response CSS support

py3: port fetch and shell commands, and review + enable already passing test_closespider.py and tests/test_utils_template.py

fix engine tests - this callback (spider_closed_callback) should accept one argument, but the error was hidden on py2

[MRG+1] Remove --lsprof command-line option. 

[MRG+1] Add Python 3.5 tox env + Python 3.5 tests in Travis

[MRG+1] Py3: port downloader cache and compression middlewares

[MRG+1] Cleanup http11 tunneling connection after #1678

[MRG+1] optional_features has been removed

[MRG+1] Support anonymous S3DownloadHandler (boto) connections