Update CHANGELOG for 2.1.0

CHANGELOG

@@ -1,3 +1,23 @@
+# 2.1.0
+
+* New Binary Delta format (version 3)
+  * Features a custom and more efficient container format, migrating away from the deprecated xar format (Zorg) (#2051)
+  * Adds compression options for lzma, bzip2, zlib, lzfse, lz4, and no compression (Zorg) (#2051)
+  * Changes default format compression from bzip2 (in version 2) to lzma (in version 3) resulting in smaller deltas (Zorg) (#2051)
+  * Tracks renames and binary diffs for files that have moved around to new locations using intelligent heuristics (Zorg) (#2051, #2053)
+  * Added more unit tests, UI tests, and generate_appcast/BinaryDelta tools support for the new format (Zorg) (#2052, #2054)
+* Fix progress bar and button alignment for checking updates (Zorg) (#2066)
+* Fix unsteady progress when installing updates (Zorg) (#2072)
+* Check http statusCode in didFinishDownloadingToURL (Eric Shapiro, Zorg) (#2049, #2073)
+* Fix version compare not treating '2.1.0' and '2.1' as being equal (Zorg) (#2065)
+* Add verify and account options for signing updates (Zorg) (#2074)
+* Add delta patch and Apple code signing verification in generate_appcast (Zorg) (#2076, #2077)
+* Use more modern NSSecureCoding APIs when available (Zorg) (#2058)
+* Use more modern FileManager APIs for copying files (Zorg) (#2059)
+* Fix make release failing when customizing XPC_SERVICE_BUNDLE_ID_PREFIX (Zorg) (#2060)
+* Preserve the Entitlements directory in podspec (digitalMoksha) (#2062)
+* Add hidden option to generate_appcast to set max CDATA threshold (Zorg) (#2075)
+
 # 2.0.0
 
 * Support for Sandboxed Applications (Zorg)