DOC: Update Changelog

Author: effigies

Changelog

@@ -24,6 +24,38 @@ Gerhard (SG) and Eric Larson (EL).
 
 References like "pr/298" refer to github pull request numbers.
 
+Upcoming release
+================
+
+New features
+------------
+* ``nib-diff`` command line tool for comparing image files (pr/617)
+  (Chris Cheng, reviewed by Yaroslav Halchenko, Pradeep Raamana and CM)
+
+Enhancements
+------------
+* Speed up reading of numeric arrays in CIFTI2 (pr/655) (Michiel Cottaar,
+  reviewed by CM)
+
+Bug fixes
+---------
+* Deterministic deduction of slice ordering in degenerate cases (pr/647)
+  (Yaroslav Halchenko, reviewed by CM)
+* Allow 0ms TR in MGH files (pr/653) (EL, reviewed by CM)
+* Allow for PPC64 little-endian long doubles (pr/658) (MB, reviewed by CM)
+* Correct construction of FreeSurfer annotation labels (pr/666) (CM, reviewed
+  by EL, Paul D. McCarthy)
+
+Maintenance
+-----------
+* Fix semantic error in coordinate systems documentation (pr/646) (Ariel
+  Rokem, reviewed by CM, MB)
+* Test on Python 3.7, minor associated fixes (pr/651) (CM, reviewed by Gregory
+  R. Lee, MB)
+
+API changes and deprecations
+----------------------------
+
 2.3 (Tuesday 12 June 2018)
 ==========================