Upgrade Composer Version (Windows)

Problem:
How to upgrade the composer version on Windows.
e.g. Warning: This development build of composer is over 60 days old. It is recommend
ed to update it by running "C:\ProgramData\ComposerSetup\bin\composer.phar self-
update" to get the latest version.

Solution:
Run the following on the command line (assumed composer is in path):
composer self- update