MEI 5 release and development services

[th-we]

Hi @ahankinson and @rettinghaus, I want to give an update about Sibmei at the community forum on March 10th. It would be great to have the MEI 5 release ready by then. I think the last thing to do for this is eliminating the (misleading) libmei field from the extension API (#268, #281).

As development only really advances when we have a project that funds features, bugfixes or extensions, would it be O.K. for you if we place a note concerning our services in the README? Something like: "Paid support and development of features, improvements and extensions are available from Notengrafik Berlin."

[rettinghaus]

I'm happy to draft a new release. Will this then be version 5?
Also I'm not generally opposed to your proposed note in the README.