Fix: Updated Slack Invite Link (#1712)

* Updated Slack Invite Link

* Restricted jsonschema to Python 2

* Forced pyrsistent to 0.16 in Python 2

* Reverted Changes to enum34

Author: CoshUS

README.md

@@ -87,7 +87,7 @@ Read the [SAM Documentation Contribution Guide](https://github.com/awsdocs/aws-s
 started. 
 
 ### Join the SAM Community on Slack
-[Join the SAM developers channel (#samdev)](https://join.slack.com/t/awsdevelopers/shared_invite/enQtMzg3NTc5OTM2MzcxLTIxNjc0ZTJkNmYyNWY3OWE4NTFiNzU1ZTM2Y2VkNmFlNjQ2YjI3YTE1ZDA5YjE5NDE2MjVmYWFlYWIxNjE2NjU) on Slack to collaborate with fellow community members and the AWS SAM team.
+[Join the SAM developers channel (#samdev)](https://join.slack.com/t/awsdevelopers/shared_invite/zt-h82odes6-qYN2Cxit7hBGIvC6oMjGpg) on Slack to collaborate with fellow community members and the AWS SAM team.
 
 
 

requirements/base.txt

@@ -1,3 +1,4 @@
+pyrsistent~=0.16.0; python_version<"3"
 boto3~=1.5
 enum34~=1.1; python_version<"3.4"
 jsonschema~=3.0