[IoT State Channels] Upgrade to go-perun v0.9.0

[manoranjith]

Description

Implements #249.

Category

Implementation Task

Relevant issue

249

Testing

All existing tests should run.

Steps to run the tests

Checklist

• [x] Name is added to the NOTICE file, if it is not present already.
• [x] Changes are rebased onto the target branch.

[manoranjith]

Updated the Readme, as discussed. Could you add your review again ? @danielksan81