Tidy up fastly configure text output

[phamann]

TL;DR

Fixes #27 to prevent the value of a API token supplied by an environment variable being rendered in the output and clean-up the output to be more consistent with other commands:

• Use progress writer to update progression through validation and persistence steps.
• Use text.Description to output the config file location
• Move config file location before success message as this was confusing some users.

Example:

[pteichman]

Nice, I like having separate output depending on where the token came from.

👍