downloads: Rewind file objects correctly on redirects.
Basic host blocker implementation.

Squashed commit of the following:

commit 8d38e9c2f13778fe21cc2c1d61c5d26907b469ef
Author: Florian Bruhin <git@the-compiler.org>
Date:   Mon Nov 24 21:04:30 2014 +0100

    Fix default adblock lists.

commit a734b87e753daec28fa0c6643af8de088041179a
Author: Florian Bruhin <git@the-compiler.org>
Date:   Mon Nov 24 21:04:14 2014 +0100

    Fix error output on adblock errors.

commit 15bc10f605ebb86c12523bb81b55d1440fcacdbf
Author: Florian Bruhin <git@the-compiler.org>
Date:   Mon Nov 24 07:38:47 2014 +0100

    Update adblock docks

commit 475d530ee50f52295c2171208c6a0278750cf4b4
Author: Florian Bruhin <git@the-compiler.org>
Date:   Mon Nov 24 07:38:39 2014 +0100

    Remove adblock ram calculation

commit 0e52cc3ec93912fd3fa3ecf6de833aef0c540a60
Author: Florian Bruhin <git@the-compiler.org>
Date:   Mon Nov 24 07:03:11 2014 +0100

    Adjust docs for hosts-file.

commit 941df242d38300d7e42a26f2e67cfd668c6f8590
Author: Florian Bruhin <git@the-compiler.org>
Date:   Mon Nov 24 06:55:40 2014 +0100

    Add logging for host blocking.

commit 4ca1561ccf32affb8439113f4f1c222d7dee1e14
Author: Florian Bruhin <git@the-compiler.org>
Date:   Mon Nov 24 00:11:59 2014 +0100

    Don't do adblock updates automatically after changing config.

commit 26d4e86ca393d4a1a5fd8fac7729ce9c2e7cd240
Author: Florian Bruhin <git@the-compiler.org>
Date:   Thu Nov 20 19:58:32 2014 +0100

    adblock: Don't delete blocked hosts between files.

commit c7af08c68adf3c135d5a2fc746eb6d3c715b0711
Author: Florian Bruhin <git@the-compiler.org>
Date:   Thu Nov 20 19:58:22 2014 +0100

    adblock: Add comments for rewinding.

commit 9af87313088cd79ab8c022bcee9308511d6328f0
Author: Florian Bruhin <git@the-compiler.org>
Date:   Thu Nov 20 19:56:39 2014 +0100

    adblock: Rewind files properly.

commit 7f3dadc04ba68c92d6789ecf5822f7b2dfc367a0
Author: Florian Bruhin <git@the-compiler.org>
Date:   Thu Nov 20 19:40:18 2014 +0100

    Add untested file support.

commit 334c01867d510b599d94c9397097a1d789c0c64c
Author: Florian Bruhin <git@the-compiler.org>
Date:   Wed Nov 19 22:33:25 2014 +0100

    adblock: Handle download errors correctly

commit 3a9af4cd4a903386dc323640f1d52e03383b3aa7
Author: Florian Bruhin <git@the-compiler.org>
Date:   Wed Nov 19 22:23:04 2014 +0100

    adblock: Add error handling for invalid input.

commit 5934c3c027ff9205adb512aab396ca913b31e50d
Author: Florian Bruhin <git@the-compiler.org>
Date:   Wed Nov 19 22:22:47 2014 +0100

    adblock: Handle done_count correctly.

commit 3ba5e83fda9b7d764bfcf1e4b1aa479daae39791
Author: Florian Bruhin <git@the-compiler.org>
Date:   Wed Nov 19 21:18:10 2014 +0100

    Read adblock files when they finished downloading.

commit 86a5ecf194445e2ebe0cf22b59e24223387880c5
Author: Florian Bruhin <git@the-compiler.org>
Date:   Wed Nov 19 20:51:25 2014 +0100

    Add hosts-file.net to host-block-lists.

commit 121f0bff953497449c32e45e671b71d954beed4c
Author: Florian Bruhin <git@the-compiler.org>
Date:   Wed Nov 19 20:51:13 2014 +0100

    Add zip-file support to adblock.py.

commit f1c0e67cb9d890a44a1d1f545ace997f0a453f91
Author: Florian Bruhin <git@the-compiler.org>
Date:   Mon Nov 17 07:41:14 2014 +0100

    print line counts for debugging

commit 75dbb8964fd44862abc378ef26fb47f8cda6061e
Author: Florian Bruhin <git@the-compiler.org>
Date:   Fri Nov 14 19:22:20 2014 +0100

    Use statusbar messages for adblock

commit 74d9142d831496e02c5baae72c2723e320af1778
Author: Florian Bruhin <git@the-compiler.org>
Date:   Fri Nov 14 08:34:46 2014 +0100

    Add basic adblock functionality.
Remove unused import
Merge branch 'master' of ssh://tonks/qutebrowser