updated dependencies

[InoMurko]

As per #63 this is the minimal code change for dependency upgrade, including support for elixir 1.6 by downgrading exdoc.

[InoMurko]

@Azolo I applied some changes, please take another look when you can.

[Azolo]

I'm really bothered about taking the tests out.

If you don't mind me taking a look and seeing how I could implement them with Cowboy 2.0.

But I really do appreciate the upgrading of Cowboy. 😄

[InoMurko]

I've added another commit, upgrading cowboy to 2.6.

To regards to the test you're referring to... The test used to use the returned req object that exposed access to the socket. The new req object currently looks like:
https://ninenines.eu/docs/en/cowboy/2.6/manual/cowboy_req/

req() :: #{
    method  := binary(),               %% case sensitive
    version := cowboy:http_version() | atom(),
    scheme  := binary(),               %% lowercase; case insensitive
    host    := binary(),               %% lowercase; case insensitive
    port    := inet:port_number(),
    path    := binary(),               %% case sensitive
    qs      := binary(),               %% case sensitive
    headers := cowboy:http_headers(),
    peer    := {inet:ip_address(), inet:port_number()},
    sock    := {inet:ip_address(), inet:port_number()},
    cert    := binary() | undefined
}

None of which allow you to upgrade the current connection manually.

[InoMurko]

Ping.

[Azolo]

Hey, sorry been swamped. I'll set a reminder to take another look at this next week.