Set logging level

[blitzmann]

As a feature request, it would be nice to set a logging level for the Bullhorn CLI. Specifically for the extensions install command, which pumps out the JSON file that it's going to POST to bullhorn, as well as the extension object that results from that POST. This is usually needlessly verbose, and it owuld be nice to be able to set a logging level that simply tells me the steps that the CLI is going through