Release 1.4.0

This release updates the dependencies used by the library and fixes badly formed test data.

We use Enmime to parse the raw email (.eml) files and enmime is no longer as lenient about badly formed header lines such as illegal characters, or missing : from header names. This is the way it should be (at least these days), so the test data was corrected.

As of this release, if you wish to parse and analyze old email archives, you will need to perform a little pre-processing.

Fix test dataset

test: fix corrupted date header in sample messages (@rjarry)

New functionality for single emails

Adds a new function allowing threading based upon a single email that leaves placeholder nodes in tact.

Also improves handling of bad References: headers in test and example, which might be useful to others.

Example improvements - trivial bug fix

Shows how to use References for threading instead of subject only.

With our horribly broken (deliberately) test set, some threads will be discarded as indecipherable, that can be tracked with the use of Subject only. The example now shows that bad link cycles will be discarded. Knowing what is discarded, you can decide what to do with emails that cannot be threaded (for instance, thread by subject instead).

Adds more complete example and fixes links in docs

Provides a more complete interface for the visualize example and fixes

documentation to match.

Stable production release

Implements a stable Threadable interface
Implements a Sort function
Implements a Walk function for tree traversal
Provides full documentation and examples
Passes the full set of go report utilities (when that site is working anyway)

Test release before stable release

The code is ready for stable release, but in order to make sure that all the various tools that analyse the code on the internet, and construct documentation etc all work, this is a final pre-release just to check that, as there needs to be a release for every external tool to work.

Initial, not quite production release

This is the initial, working, not quite production but very nearly release. There should
be no bugs if the tests are good enough. It is good enough for production, but be aware
that the 1.0.0 release may introduce a few tweaks, such as a generic sort for instance.