udpate crt-python to 0.6.2 (#97)

Co-authored-by: Dengke Tang <dengket@amazon.com>

Author: TingDaoK

setup.py

@@ -13,7 +13,7 @@
     url='https://github.com/aws/aws-iot-device-sdk-python-v2',
     packages = ['awsiot'],
     install_requires=[
-        'awscrt==0.6.1',
+        'awscrt==0.6.2',
         'futures;python_version<"3.2"',
         'typing;python_version<"3.5"',
     ],