Add verbose mode

[nickthecook]

It would be helpful to have a verbose mode, either in the options section of ops.yml, as a command-line option like -v, or both.

Verbose mode should print things like:

• where ops looks for secrets files, and whether it finds them
• where ops looks for app config files, and whether is finds them
• what ENV vars ops loads
• what commands ops runs to satisfy dependencies

[nickthecook]

Also:

• the stdout/stderr of dependencies as they are met, for dependencies that hang or take a long time