Bopmatic Tech Preview (v0.20.0)

Add 'logs' subcommand for retrieving service logs

Server side logs can now be retrieved via the following usage:

```
Usage:
  bopmatic logs [--projname <projectName>] [--svcname <serviceName>] [--starttime <startTime>] [--endtime <endTime>]

Flags:
  --projname                         Bopmatic project name; when run from a Bopamtic project
                                     directory this will default to your current Bopmatic
				     project's name
  --svcname                          Service name within your Bopmatic project; this will
                                     default to your current Bopmatic project's only service
				     if there is only one
  --starttime                        Start time of log retrieval (in UTC); default 48h ago
  --endtime                          End time of log retrieval (in UTC); default now
```

For example:
```
  $ bopmatic logs --projname myhello --svcname Greeter
```