Adding support to local endpoints

[nicxlau]

When using local endpoints like localhost or the ID of a docker container are passed, https is always appended to the endpoint.

Example of how it is currently happening:

$connection = new Connection(['endpoint' => 'example-container']); // https://example-container
$connection = new Connection(['endpoint' => 'example-container:8000']); // https://example-container:8000

This PR prevent it.

[kitar]

Thank you for the suggestion, @nicxlau ! Could you please try to see if this issue is resolved with #41?