Bump into php-7.1+ versions

[peter279k]

As title, the php-7.1 versions have been released for the while.

And I think it's time to consider bumping into the php-7.1+ versions now.

To do this issue, I think we should consider following points:

• Upgrade the necessary dependencies to the current released versions. Such as Guzzle.
• Checking the syntax and modify them to be compatible with the php-7.1+ versions.

[ricbra]

Thank you for opening this issue. Is this something you want to work on?

[peter279k]

Hi @ricbra, thank you for your reply/concern.

If this issue is accepted, I can work on this :).

[ricbra]

Yes sure, I'm not working actively anymore on this so if someone wants to step in 👍