Incompatible with oauth2 extension

[maikschneider]

When using the ext-oauth2-client extension, the login process throws an In2code\Instagram\Exception\ConfigurationException.

This is due to the identical query parameter code in the returnUrl which the GetAuthenticationCode middleware falsely interprets the request as an authentication redirect of instagram.

Since the oauth redirect contains more parameter than just code, I would add an additional check for the amount of parameters in the isInstagramAuthentificationRedirect.

PR will follow.

[maikschneider]

Ah, same issue as in #16

Checking the referrer is even better. Will adopt this.

[maikschneider]

Update: The pull request does not fix the issue.