Update disclaimer for 1.1 release

DISCLAIMER.md

 Disclaimer
 ==========
 
-This software is preliminary or provisional and is subject to revision. It is
-being provided to meet the need for timely best science. The software has not
-received final approval by the U.S. Geological Survey (USGS). No warranty,
-expressed or implied, is made by the USGS or the U.S. Government as to the
-functionality of the software and related material nor shall the fact of release
-constitute any such warranty. The software is provided on the condition that
-neither the USGS nor the U.S. Government shall be held liable for any damages
-resulting from the authorized or unauthorized use of the software. Any use of
-trade, firm, or product names is for descriptive purposes only and does not
-imply endorsement by the U.S. Government.
+This software has been approved for release by the U.S. Geological Survey
+(USGS). Although the software has been subjected to rigorous review, the USGS
+reserves the right to update the software as needed pursuant to further analysis
+and review. No warranty, expressed or implied, is made by the USGS or the U.S.
+Government as to the functionality of the software and related material nor
+shall the fact of release constitute any such warranty. Furthermore, the
+software is released on condition that neither the USGS nor the U.S. Government
+shall be held liable for any damages resulting from its authorized or
+unauthorized use. Any use of trade, firm, or product names is for descriptive
+purposes only and does not imply endorsement by the U.S. Government.