doc: update readme.md to use new version of -help output command

cmd/migrate/README.md

@@ -86,14 +86,18 @@ Options:
   -help            Print usage
 
 Commands:
-  create [-ext E] [-dir D] [-seq] [-digits N] [-format] NAME
-               Create a set of timestamped up/down migrations titled NAME, in directory D with extension E.
-               Use -seq option to generate sequential up/down migrations with N digits.
-               Use -format option to specify a Go time format string.
+  create [-ext E] [-dir D] [-seq] [-digits N] [-format] [-tz] NAME
+           Create a set of timestamped up/down migrations titled NAME, in directory D with extension E.
+           Use -seq option to generate sequential up/down migrations with N digits.
+           Use -format option to specify a Go time format string. Note: migrations with the same time cause "duplicate migration version" error.
+           Use -tz option to specify the timezone that will be used when generating non-sequential migrations (defaults: UTC).
+
   goto V       Migrate to version V
   up [N]       Apply all or N up migrations
-  down [N]     Apply all or N down migrations
-  drop         Drop everything inside database
+  down [N] [-all]    Apply all or N down migrations
+        Use -all to apply all down migrations
+  drop [-f]    Drop everything inside database
+        Use -f to bypass confirmation
   force V      Set version V but don't run migration (ignores dirty state)
   version      Print current migration version
 ```