Bump version for 6.1.0 release (#1168)

* Bump version for release

* Update release date; targeting Wednesday 3rd June for release

* Update release date

* Update PR count

Author: mdickinson

CHANGES.rst

@@ -4,7 +4,7 @@ Traits CHANGELOG
 Release 6.1.0
 -------------
 
-Released: 2020-05-XX
+Released: 2020-06-05
 
 The Traits library is a foundational component of the Enthought Tool Suite. It
 provides observable, typed attributes for Python classes, making those classes
@@ -139,7 +139,7 @@ future changes:
 Detailed PR-by-PR changes
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 
-More than 150 PRs went into this release. The following people contributed
+More than 160 PRs went into this release. The following people contributed
 code changes for this release:
 
 * Ieva Cernyte

setup.py

@@ -22,7 +22,7 @@
 MINOR = 1
 MICRO = 0
 PRERELEASE = ""
-IS_RELEASED = False
+IS_RELEASED = True
 
 # If this file is part of a Git export (for example created with "git archive",
 # or downloaded from GitHub), ARCHIVE_COMMIT_HASH gives the full hash of the