connection's subscriptions injected into context

Adding subscription 'connection' into the context as it is done with requests for queries and mutations.

Forwarding headers request

• Modify the default headers to forward per Request
• Increase test coverage & cases

Removing request package from schema loader

removing request and request-promise dependencies (#9)

Co-authored-by: Ivan Martinez Pupo <[email protected]>

GrapgQl gateway initial release

v1.0.6

adding node-fetch dependency