http client: option to not raise errors

Pass raise_error=False to the fetch method to disable the raising of
HTTPError on errors.
use the same protocol when redirecting to default host
Merge pull request #1260 from lilydjwg/no-handler-redirect

use the same protocol when redirecting to default host
swap platform.system() for sys.platform; #1263
Merge pull request #1264 from nbargnesi/master

swap platform.system() for sys.platform
Merge pull request #1258 from tdyas/no_raise_error

http client: option to not raise errors
fix test_request_timeout on Windows by increasing timeout
tox: add optional pyxx-no-ext environments

These can be run on systems without an available C compiler.
Merge pull request #1268 from schlamar/win-timeout

fix test_request_timeout on Windows
Merge branch 'master' into fix-ipv6-host
remove executable permission from tornado.web
move code to seperate function 'split_host_and_port'