Squashed commit of the following:

commit 6a1aabf0db6dc90da47e7bea812a6e3a951546c0
Author: Quba1 <[email protected]>
Date:   Sat Oct 2 16:53:11 2021 +0200

    update documentation

commit 0e10b7a30e9f54fb1cfd786c38f4597f7d84f07f
Author: Quba1 <[email protected]>
Date:   Sat Oct 2 16:06:09 2021 +0200

    clippy corrections

commit d1b5e50
Author: Quba1 <[email protected]>
Date:   Sat Oct 2 15:59:34 2021 +0200

    add key writing and writing to file

commit 68ef0fb
Author: Quba1 <[email protected]>
Date:   Sat Oct 2 14:55:26 2021 +0200

    BUGFIX

    clone message in iterator instead of soft copy

commit e5efb50
Author: Quba1 <[email protected]>
Date:   Fri Oct 1 19:54:51 2021 +0200

    add file writing

commit 97bd764
Author: Quba1 <[email protected]>
Date:   Fri Oct 1 19:22:55 2021 +0200

    reorganise keyed_message files

Bugfix

The memory allocated by ecCodes were not correctly freed.
codes_handle_delete is now called for each iterator step

adding pub use of FallibleIterator

crate users do not need to import that crate manually

Squashed commit of the following:

commit a0e9bb7fb22df952a5ccd18e82e523c69bf2090b
Author: Quba1 <[email protected]>
Date:   Mon Sep 27 14:15:29 2021 +0200

    update tokio and version

commit 0dc98b4c322a81b66ac95259d90afa53948719a8
Author: Quba1 <[email protected]>
Date:   Mon Sep 27 14:10:36 2021 +0200

    add test with gfs data and bugfix read_key

commit c22169bd5562357e9254d5c9658a81330d6a85de
Author: Quba1 <[email protected]>
Date:   Mon Sep 27 13:47:15 2021 +0200

    add gfs data for tests

version update

clippy

dependency and documentation update

added pre-release info