update release notes

RELEASE_NOTES.txt

+Release 1.11 (05/15/2018)
+=============================
+- Added support for compression and decompressing files
+  - New commands:
+    * compress-files
+    * decompress-files
+- Added support for deleting files
+  - New commands:
+    * delete-file
+    * delete-files
+- Modified stat-file utility, which now requires explicit --md5sum flag to
+  retrieve retrieve checksum
+- Added new --path-pattern option to list-files command
+- DM Station GUI fixes/enhancements:
+  - Added initial GUI test suite
+  - Added right-click copying functionality
+  - Fixed issue trailing comma for upload parameters
+  - Fixed CPU usage bug 
+  - Fixed incorrect handling of user selections
+  - Fixed focus policy for several buttons
+
 Release 1.10 (03/30/2018)
 =============================
 - Added support for command output in html format