Revert "Update CHANGES.txt"

This reverts commit 51686fa.

Author: pyahmed

pycorn/docs/CHANGES.txt

@@ -1,7 +1,3 @@
-v0.18
-======
-- fixed xmin being ignored when 0
-
 v0.17
 ======
 - Added experimental support for extracting and plotting UNICORN6 zip bundles
@@ -54,4 +50,4 @@ v0.11
 
 v0.1
 ======
-- Initial release
+- Initial release