Updated dependencies to fix Excessive Platform Resource Consumption w…

…ithin a Loop in Kubernetes: https://github.com/mvmaasakkers/certificates/security/dependabot/1

Tagged v0.7.1. This is a very tiny clean up release.

Upped go version to 1.18 and updated dependencies

Added external csr signing option, fixes #23

Changed go version to 1.13

Add more verbose error messages