Update Dependencies

MERGE REQUEST

Overview

Update the Sia dependencies. A couple of our upstream repos have pushed changes, including our own merkletree repo. This MR updates all of the dependencies and also moves to requiring go1.13

Checklist

Review and complete the checklist to ensure that the MR is complete before assigned to an approver.

• All new methods, or updating methods have clear docstrings
• Testing added or updated for new methods
• Any new packages are added to Makefile and .gitlab-ci.yml
• API documentation updated for API updates
• Module README.md updated for changes to work flow
• Issue added to Sia-UI repo for new supporting features
• Changelog updated