Add ability for build sub-command to stream log output

[dogonthehorizon]

As a Bartlett user, I would like to stream log output directly from the build sub-command, so that I do not have to execute a second log sub-command when triggering jobs in order to stream log output.

AC:

• Flag added (-f|--follow) to build sub-command to stream log output

[dogonthehorizon]

Current implementation can be found here:
https://github.com/Nike-Inc/bartlett/tree/feature/build-follow-log-output

It works...ish, see commit log for more info.