Merge pull request #1372 from cuthbertLab/update-version-docs

Update version docs

music21/_version.py

@@ -5,8 +5,7 @@
 As of v.2.0.0, Music21 uses something close to the principles of Semantic Versioning, we'll
 try very hard so that X.Y.Z have meanings about changes to the system.
 Changes in X represent changes that will break old features.
-New Y numbers add new features; Z -- bug fixes.  This means that the X number
-will change more often than before.
+New Y numbers add new features; Z -- bug fixes.  The X number change about once per year.
 
 Differences with strict semantic versioning: I won't make 100% guarantees that we'll never
 break anything without a change in the major number, esp. if the change affects a tiny
@@ -42,7 +41,7 @@
 Changing this number invalidates old pickles -- do it if the old pickles create a problem.
 '''
 
-__version_info__ = (8, 0, 0, 'a9')  # can be 4-tuple: (7, 0, 5, 'a2')
+__version_info__ = (8, 0, 0, 'a9')  # can be 3-tuple or 4+-tuple: (7, 0, 5, 'a2')
 
 v = '.'.join(str(x) for x in __version_info__[0:3])
 if len(__version_info__) > 3 and __version_info__[3]:  # type: ignore