Improve logging output, add debug

[cjonesy]

Logs will now indicate which monitor is sleeping:

2020/05/28 09:26:32 INFO: [my-first-monitor] Sleeping for 300 seconds
2020/05/28 09:26:32 INFO: [my-second-monitor] Sleeping for 300 seconds
2020/05/28 09:26:32 INFO: [my-other-monitor] Sleeping for 300 seconds

When debug is enabled (anemometer start --debug), you'll see the actual metrics in the logs:

2020/05/28 09:26:32 DEBUG: [my-first-monitor] Publishing metric - Name: my.first.metric, Value: 1, Tags: [my:tag, other:tag]
2020/05/28 09:26:32 INFO: [my-first-monitor] Sleeping for 300 seconds
2020/05/28 09:26:32 DEBUG: [my-second-monitor] Publishing metric - Name: my.second.metric, Value: 1.9999, Tags: [my:tag, other:tag]
2020/05/28 09:26:32 INFO: [my-second-monitor] Sleeping for 300 seconds

Closes #2

[joshuawscott]