Use better log formatting

[josh-padnick]

I was debugging an issue in a call to gruntwork-install, and my underlying issue was actually with the command I passed to fetch. But the logs output by fetch don't make it obvious that it's fetch throwing the error. Here's an example:

    ubuntu-ami: 2017-11-14 20:47:53 [INFO] [gruntwork-install] Success!
    ubuntu-ami: 2017-11-14 20:47:53 [INFO] [gruntwork-install] Installing from install-kafka...
    ubuntu-ami: 2017-11-14 20:47:53 [INFO] [gruntwork-install] Downloading module install-kafka from https://github.com/gruntwork-io/package-kafka
    ubuntu-ami: ERROR: You must specify exactly one of --tag, --commit, or --branch. Run "fetch --help" for full usage info.

The statement Run "fetch --help" for full usage info. is an indicator this is a fetch error, but the log message should be prefixed with the fetch name, as gruntwork-install logs are in the example above.

[robmorgan]

Fixed in https://github.com/gruntwork-io/fetch/releases/tag/v0.4.0