Add plan command node-token command

New commands:

• k3sup plan - generate an installation script across multiple nodes
• k3sup node-token - fetch the server's node-token for efficient joining of many nodes

Watch a demo on YouTube
Learn more in the docs

Changelog for 0.13.2:

• PR #416 Add plan command node-token command by @alexellis

Commits
bb4baf4 Add notes to README for k3sup plan by @alexellis
48c82b3 Use node-token from an env-var instead of a file by @alexellis
8c01ffb Use an env-var for the node-token instead of a file by @alexellis
bee8462 Update examples for k3sup plan by @alexellis
7ac93b8 Move temporary file deletion into a defer by @alexellis
2382066 Add plan and node-token commands by @alexellis
3a02867 Fix typo by @alexellis
863a0ed Alteration to support message by @alexellis

Changes: 0.13.1...0.13.2

Generated by Derek