Bump version to 0.4.0

## Overview

This release revives the connector in fact: now it supports PHP 7.0-7.4 and
Tarantool 1.6-2.5 (except 2.2 for now due to #151). There are several
restrictions, however. Most notable are:

- Schema fetching fails on a space with `is_nullable` or `collation` index
  part parameters (#151).
- New call_17 command is not supported yet (#101).

Those problem will be fixed in the next release. Anyway, this release allows
to upgrade PHP and Tarantool versions and keep existing PHP code, which uses
the connector, operational.

## Breaking changes

This release should not break existing code.

## New features

- Support PHP 7.3 and 7.4 (#139, #150).

## Bugfixes

- Ignore unknown fields in a space format (PR #132).
- Fixed 'Undefined property' error at attempt to extend Tarantool class
  (#135).
- Raise 'No field ... defined' at attempt to update by an unknown field name
  (b3846f6).
- Allow `null` as `offset` value for select() when strict types are enabled
  (#154).

## Testing and deployment

- Support both Python 2 and 3 in the test runner (9bc7fa5).
- Use strict types mode in testing (da8ecba).
- Support PHPUnit 6-9 for testing against different PHP versions.
- Enabled PHP 7.0-7.4 in testing.
- Enabled Tarantool 1.6-2.5 in testing (except 2.2 for now).
- Added 'php-tarantool' alias for Debian / Ubuntu packages (PR #155).
- Enable the extension by default on Debian / Ubuntu (40d8795, PR #156).
- Deploy packages for Linux distributions with PHP 7 (#117):
  - CentOS 8;
  - Fedora 25-31;
  - Debian: Stretch, Buster;
  - Ubuntu: Xenial, Bionic, Eoan, Focal.

	Bump new version

	Fix for broken upsert/update

PHP7 support

First release for PHP7 version

Tarantool-PHP 0.1.0

Fix a lot of bugs, added upsert command, added tests

tarantool-php 0.0.13

tarantool-php version 0.0.12

tarantool-php 0.0.11, fix error on 32but systems, fix erorr, add aliases