This commit refactors the codebase to consistently use Python 3.6
f-strings for string concatenation and interpolation.

BREAKING CHANGE: This update increases the minimum required Python
version from 3.5 to 3.6. Python 3.5 reached end-of-life in September
2020 (~4 years ago) and has been dropped from most distributions, so the
impact on users should be minimal.

As discussed in #259, the `limit` parameter - to the low-level
`listing.List` and its subclasses, and to various higher-level
functions which ultimately return `List` or `GeneratorList`
instances - is confusing and misleading.

It is passed through to the API calls, and effectively specifies
how many items a single API call will return. But because our
`List` yields a single item at a time and will keep doing API
calls until the API says there's no more data, it does not limit
how many items our `List` will yield, nor specify its chunk size.
It seems natural to expect that `List(limit=10)` or
`page.revisions(limit=10)` will give you a generator that yields
only 10 items, or yields 10 items at a time, but it does not; it
gives you a generator which queries the API in chunks of 10 items
at a time, but will yield every item the API gives it, one by one.

This is probably not ever how we really intended mwclient to work
(there's an old `# NOTE: Fix limit` comment which implies as much)
but it has worked this way for 16 years, so we should probably
not change it just in case someone really has a need to specify
the API chunk size for some reason, or some code somehow happens
to implicitly rely on it behaving the way it does.

So, this keeps the behaviour of the `limit` param wherever it
exists, but triggers a deprecation warning. Everything that had
a `limit` param now also has an `api_chunk_size` param that does
the same thing, but is more explicitly named and does not trigger
a deprecation warning. And everything that had a `limit` param
now also has a `max_items` param that does what it sounds like,
and what people are more likely to want - sets an absolute limit
on the number of items the generator will yield.

For efficiency, if `max_items` is set, neither `limit` nor
`api_chunk_size` is set, and `max_items` is below
`site.api_limit`, we set the API chunk size to `max_items` so
we only retrieve as many items as we actually need.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

As discussed in #197, this renames the `reqs` argument to `Site`
to `connection_options`. The old name still works but triggers a
DeprecationWarning. If you specify both we raise ValueError.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

Signed-off-by: Adam Williamson <awilliam@redhat.com>

- Move the auth anchor to be above the correct section
- Add missing anchors so all sections have them
- Add blank line above the old_login anchor and use hyphen instead of _.

This fixes the warning:

DeprecationWarning: Specifying host as a tuple is deprecated as of mwclient 0.10.0. Please use the new scheme argument instead.

Use and recommend format from RFC 7231.
Give examples for custom User-Agent strings.

Closes #49

This is what is imported at the beginning of the examples.
This could also be done by changing the import to 'import mwclient'
rather than 'from mwclient import Site'.

Neither seems more correct but I have tried to follow
what seems most intended.

>>> from mwclient import Site
>>> site = mwclient.Site('en.wikipedia.org')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'mwclient' is not defined

vs.

>>> site = Site('en.wikipedia.org')
>>> page = site.pages['Greater guinea pig']
>>> text = page.text()
>>> page.exists
True

- https is standard now, so no need to explicitly declare that
- wrap lines around 90 chars
- minor rewriting

to adher to 52b9d8b8

- Adds link to the user guide from readme
- Adds a new page to the user guide on "working with files"

Add OAuth and update docs

- Remove :ref:s from the headers, since they made the latex build crash
- Add logo

Remaining issue:

- Can't get headings levels right on both the html and the latex builds
  at the same time. More info in #40