Bump reqwest & hyper and allow http2 negotiation

[jqnatividad]

Somewhat duplicative of #124, but also went ahead to add the ability to transparently negotiate upgrading to an HTTP2 connection, which all the backends support.

[jaemk]

thanks @jqnatividad ! Would you mind resolving the cargo toml conflicts - and also reverting the space alignment (I don't like having to update a bunch of lines to fix alignment when one line changes, unless it's some ascii table)

[jqnatividad]

DONE @jaemk !

In hindsight, shouldn't have applied the BetterTOML format... force of habit, as it helps with the giant Cargo.toml I have for my project. :)