Asynctnt

**Bugs fixed:**
* Show a diag message rather than Lost connection to Tarantool when disconnected (closes [19](https://github.com/igorcoding/asynctnt/issues/19))

**Other changes:**
* Updated Cython to 0.29.21
* Building wheels for Python 3.9

**Bugs fixed:**
* Fixed hanging PushIterator when connection to Tarantool is lost ([17](https://github.com/igorcoding/asynctnt/issues/17)).

**New features:**
* Parse autoincrement ids in sql response ([14](https://github.com/igorcoding/asynctnt/issues/14)). Thanks to oleynikandrey
* Added Python 3.8 support. Removed all redundant `loop` arguments to functions
and asyncio classes.

**Other changes:**
* Updated Cython to 0.29.14
* Updated msgpuck to most recent version.
* Added building wheels for Windows for Python 3.6, 3.7, 3.8

**Breaking changes:**
* Removed method `body2yaml` from Response.
* Option `tuple_as_dict` is removed from `Connection` and all the methods.

**New features:**
* Making Response objects contain TarantoolTuple objects if format information
is available either in space or in response from Tarantool (closes [3](https://github.com/igorcoding/asynctnt/issues/3)).
* TarantoolTuple objects are index-agnostic, meaning one can access tuple value
either by numeric index or by a key from `space:format()` specification.
* You can directly access Response using indices
(`resp[0]` instead of `resp.body[0]`).
* Added supported for receiving `box.session.push()` messages from Tarantool
by introducing new parameter `push_subscribe` to api methods in `Connection`
and the PushIterator class to iterate over the push messages of a specific
request.
* Added `Connection.sql` method to execute SQL statements for Tarantool 2
(see asynctnt docs for details).
* Added internal background coroutine with pings periodically a Tarantool
instance to check if it is alive and to refresh schema if it is changed
(default period is 5 seconds and is configured by `Connection.ping_timeout`
parameter).

**Changes:**
* Iteration over TarantoolTuple results in iterating over a raw tuple by
indices.
* TarantoolTuple has `.keys()`, `.values()` and `.items()` from the dict
protocol. All these methods return iterators making it possible to iterate
over keys, values or key-value pairs accordingly. `keys` and `items` methods
ignore any extra fields if space format contains less fields than there are
in the tuple. One can acces those extra fields by index numbers.
* `Connection`'s default `connect_timeout` changed from `60` to `3` seconds.
* `select`: changed default iterator type to `ALL` if no key provided
(fixes [2](https://github.com/igorcoding/asynctnt/issues/2))
* `Response` new function `done()` indicates if Response is
actually finished.
* `schema_id` is not being sent to Tarantool to check against current schema
version. Instead schema is only checked and refetched if needed only _after_
the request. This ensures that request is executed in a "constant" time
rather than unpredicted with possible schema changes.
* Improved `Connection.refetch_schema()` method to ensure there is only one
currently running refetch process.

**Other changes:**
* `asynctnt` now ships with precompiled wheel packages.
* Changed version numbering.
* Updated `Cython` to version `0.29`
* Updated `msgpuck` version
* Improved speed of asynctnt method calls a bit more

**Changes:**
* Improved and simplified connect/reconnect process
* Added ContextManager async with protocol for Connection
* Added `is_fully_connected` property to Connection
* Added disconnect Lock

**Bugs Fixed:**
* Auto reconnect misbehaved on double on_connection_lost trigger ([11](https://github.com/igorcoding/asynctnt/issues/11))