[Nexus] NeXus definitions release v3.3 is ready to be tagged

[Pete Jemian]

As indicated in the Milestone 
(https://github.com/nexusformat/definitions/milestone/4), the next 
release of the NeXus definitions (v3.3) is ready to be tagged.  Release 
notes have been added to the repository 
(https://github.com/nexusformat/definitions/blob/master/release-notes.md).

The release date is planned for July 13, after the next teleconference 
call.  (http://www.nexusformat.org/Telco_20170711.html)

If you have additional matters to be addressed in this release, please 
file a new issue: https://github.com/nexusformat/definitions/issues/new 
and mark it with the "NXDL 3.3" milestone.  At this time, the only issue 
remaining in that milestone is to tag the new release.

A milestone for the following release (v3.4) has been set for 
2018-01-01.  Already, there are 29 issues assigned to this release.

Regards,
    Pete