Add ability to opt-out of writing metadata to fastly.toml

[kpfleming]

For automated publishing processes, writing to fastly.toml is not valuable as the results will be thrown away as soon as the process is completed.

[harmony7]

This feature has been released as part of v7. #37

The publish process is now run in either of two modes: against the simulated local KV Store or against the real KV Store based on the presence of the --local flag.