Bump version to 1.3.0-rc1

First pre-release for v1.3.0.

Signed-off-by: David Brown <david.brown@linaro.org>
diff --git a/scripts/setup.py b/scripts/setup.py
index 0ec2cd9..67cca9f 100644
--- a/scripts/setup.py
+++ b/scripts/setup.py
@@ -2,7 +2,7 @@
 
 setuptools.setup(
     name="imgtool",
-    version="1.2.0",
+    version="1.3.0",
     author="The MCUboot commiters",
     description=("MCUboot's image signing and key management"),
     license="Apache Software License",