Adds support to X-Insta-Forwarded-For header

The X-Insta-Forwarded-For HTTP header is optional, but recommended for any app making server-side calls. To enable this setting, edit your OAuth Client configuration and mark the Enforce signed requests checkbox. When enabled, Instagram will check for the X-Insta-Forwarded-For HTTP header and verify its signature. The expected value is a combination of the client's IP address and a HMAC signed using the SHA256 hash algorithm with your client's IP address and Client Secret.