!191 Update version number to rc1

From: @pkuliuliu
Reviewed-by: @jxlang910,@liu_luobin
Signed-off-by: @jxlang910

setup.py

@@ -20,7 +20,7 @@ from setuptools import setup
 from setuptools.command.egg_info import egg_info
 from setuptools.command.build_py import build_py
 
-version = '1.2.0'
+version = '1.2.0-rc1'
 cur_dir = os.path.dirname(os.path.realpath(__file__))
 pkg_dir = os.path.join(cur_dir, 'build')