Rewrote console output mechanism.
Fixed a few bugs related to YAML configuration.
Added `--response-code-only` and `--success-only` flags.
Removed title header from every request. Only shows up for errors and in --version and --help flags.
Cleaned up --concise view.
Cleaned up RestClient class by removing old references to config and env. It's agnostic to how the config and env are set.