Add methods Log::requests() and Log::clear() to ease assertions on Log client

[spawnia]

• Added automated tests
• Documented for all relevant versions
• Updated the changelog

Changes

The Log client offers a convenient method of reading the requests as structured data:

$log = new \Spawnia\Sailor\Client\Log(__DIR__ . '/sailor-requests.log');
foreach($log->requests() as $request) {
    var_dump($request);
}

array(2) {
  ["query"]=>
  string(7) "{ foo }"
  ["variables"]=>
  array(1) {
    ["bar"]=>
    int(42)
  }
}
array(2) {
  ["query"]=>
  string(7) "mutation { baz }"
  ["variables"]=>
  NULL
}

To clean up the log after performing tests, use Log::clear().

Breaking changes

None.