[MRG] DOC Remove "Ubuntu" section from sidebar/ToC

As described in http://www.sphinx-doc.org/en/latest/markup/misc.html#metadata

[MRG+1] Add middleware to template project (closes #2335)

[MRG+1] Document `download_latency` meta key

[MRG+1] LinkExtractor PY3 'unicode' type fix

[MRG+1] Add better messages for when response content isn't text (closes #2264)

[MRG+1] Update conda channel to conda-forge and show conda version badge.

Test Slot's heartbeat state before stopping it

Also add a test on state of looping task in LogStats extension

Fixes #2011 and #2362

Document update in "Using Firefox for scraping"

Fix typo in media pipeline docs

[MRG+1] Update documentation to explain the use of double quotes on Windows (fixes #2325)

[MRG+1] doc: wording

Fix tutorial AuthorSpider

Thx for your advice.

In the AuthorSpider, original css selector failed to get links of author pages

Update release notes for upcoming 1.2.1

Typo (through was misspelled)

[MRG+1] Added documentation about accessing header values

[MRG+1] Better explain middleware orders and processing directions

* Do not interpret non-ASCII bytes in "Location" and percent-encode them

Fixes GH-2321

The idea is to not guess the encoding of "Location" header value
and simply percent-encode non-ASCII bytes,
which should then be re-interpreted correctly by the remote website
in whatever encoding was used originally.

See https://tools.ietf.org/html/rfc3987#section-3.2

This is similar to the changes to safe_url_string in
https://github.com/scrapy/w3lib/pull/45

* Remove unused import