msgthr 1.1.0 - simplify usage

msgthr 1.1.0 - simplify usage

This release simplifies the API to avoid (and raise on) user
errors.  If your code worked with previous versions, there
are no changes necessary to make.

This release fixes our API to match the documentation in making
Msgthr#order! optional.  Furthermore, the block previously
passed to Msgthr#order! may now be passed to Msgthr#thread!
instead.

For users who truly do not care about ordering, Msgthr#walk_thread
may be called immediately after the last call to Msgthr#add.

Thanks to Dimid Duchovny for the feedback which led to this release:
https://80x24.org/msgthr-public/CANKvuDc2mkxLuh+3+WXWfMXzxK2bShNesrD5xLocGOD1RybbwQ@mail.gmail.com/