Merge pull request #3 from lucasrc/hotfix/attrs_update

fix: TypeError "unhashable type: "EncryptedDataKey"

Author: mattsb42-aws

setup.py

@@ -31,7 +31,7 @@ def get_version():
     install_requires=[
         'boto3>=1.4.4',
         'cryptography>=1.4.0',
-        'attrs>=16.3.0'
+        'attrs==16.3.0'
     ],
     classifiers=[
         'Development Status :: 5 - Production/Stable',