Don't use spinner, colored output and emojis when output is redirected

[svenmuennich]

According to this SO thread, we can just use process.stdout.isTTY.

[cjuner]

For now, this should be an improvement wrt to processing redirected output: #12

But yes, isTTY would be – non-proper TTY outputs like IDEs or automated build environments don't usually handle control characters well (e.g., deleted previous characters to delete the spinner)