Added HTTP client implementaions for stream wrapper and Guzzle with fallback to stream wrapper when curl not installed
Enabled app secret proof by default
Merge pull request #112 from SammyK/enable-app-secret-proof-by-default

Enabled app secret proof by default
Merge pull request #90 from SammyK/http-client-implementation-guzzle-and-stream

Http client implementations for stream wrapper & Guzzle with stream fallback