Add option to hide namespace in logs

[donatas]

Our log collector expects the output to be of some format (across systems, that write logs) and now the only thing I can't control is the namespace, prepended to each line.

It's enabled by default, passing environment variable allows hiding it.

PR contains tests that cover default behavior (namespace + log) and the new feature.

[donatas]

@TooTallNate please review

[coveralls]

Coverage increased (+7.06%) to 80.838% when pulling d790954 on donatas:master into 22f9932 on visionmedia:master.

[coveralls]

Coverage increased (+7.06%) to 80.838% when pulling 5bbfcb0 on donatas:master into 22f9932 on visionmedia:master.

[donatas]

@thebigredgeek @nkolban

[Qix-]

Hi there - I'm 👎 personally with adding yet another env var. Could you weigh in on #582?

[Qix-]

Closing in favor of #582.