setup.py license field should contain the license name

Author: nils-werner

setup.py

@@ -13,7 +13,7 @@
     author='Cloudpipe',
     author_email='[email protected]',
     url='https://github.com/cloudpipe/cloudpickle',
-    license='LICENSE.txt',
+    license='BSD 3-Clause License',
     packages=['cloudpickle'],
     long_description=open('README.md').read(),
     classifiers=[