OAuth extension adjusted to support any custom request type.
Redundant `yii\authclient\OpenId::sendStreamRequest()` removed.
Used substr_compare instead of substr when we don't care about result
`yii\authclient\widgets\AuthChoice` now preserves initial settings while opening popup
phpdoc
Replaced substr_compare with strncmp where possible
property code style extensions
Adjusted the location of AuthChoice assets. [skip ci]
Removed unused "use" statements
fix authchoice.js
OAuth API Response with 20x status should be in normal

Hello,

I used **Yii2 authclient** to build a Github OAuth (2.0) client, and performed a POST call to create a Github repository hook. But I got this exception:

```
exception 'yii\authclient\InvalidResponseException' with message '
Request failed with code: 201, message:
{
	"url": "https://api.github.com/repos/ychongsaytc/example/hooks/1000000",
	"test_url": "https://api.github.com/repos/ychongsaytc/example/hooks/1000000/test",
	"id": 1000000,
	"name": "web",
	"active": true,
	"events": ["push"],
	"config": {
		"url": "https://example.com/payload",
		"content_type": "form",
		"secret": null
	},
	"last_response": {
		"code": null,
		"status": "unused",
		"message": null
	},
	"updated_at": "2014-09-14T03:02:55Z",
	"created_at": "2014-09-14T03:02:55Z"
}
' in /home/ubuntu/public_html/live/vendor/yiisoft/yii2-authclient/BaseOAuth.php:206
```

I think a successful API call is not always exactly return **200** status, like **Create a hook** API of Github: https://developer.github.com/v3/repos/hooks/

It will return `201 Created` if hook was successfully created.

In my opinion, is status code starts with **20** in normal scenario?

close #5011
Removed unused bower.json files. Adjusted version dependencies.
added branch alias to composer.json
composer.json tabs -> spaces
prepare for 2.0.0-rc release.
prepare for next release.
Added ability to operate nested and complex attributes via `yii\authclient\BaseClient::normalizeUserAttributeMap`
'authclient' docs adjusted
2.0.0 release.
prepare for next release.