Add ForceOutput to write the spinner regardless of running in a TTY

[kylecarbs]

This isn't a breaking change, but relates to #131.

[kiwiz]

I've been following along the convo in #131 and I think a better solution (albeit breaking change) would be to:

• Default to printing output with a newline instead of erase control codes when the terminal isn't a TTY
  • Optionally decrease the output frequency?
• Add an option to suppress output entirely when the terminal isn't a TTY

This results in readable output and staves off timeouts in CI environments.