Feature Request: Add mechanism to interject debug output directly with reporter output

[object88]

If I have a long-running test suite with multiple browsers, and debug output as part of my test suite, I can't easily determine what debug output correlates to what reporter messages. For example:

07:40:50 ------------------------------------------------------------------
07:40:50 [firefox 47 #1m] Session ID: 1c569d4262034b3dabb8930bca632f07
07:40:50 [firefox 47 #1m] Spec: /home/jenkins/workspace/.../header.spec.js
07:40:50 [firefox 47 #1m] Running: firefox (v47)
07:40:50 [firefox 47 #1m]
07:40:50 [firefox 47 #1m]   The Navigation Header
07:40:50 [firefox 47 #1m]
07:40:50 [firefox 47 #1m]     when ...
07:40:50 [firefox 47 #1m]
07:40:50 [firefox 47 #1m]       and the ...
07:40:50 [firefox 47 #1m]           ��� takes ...
07:40:50 [firefox 47 #1m]           ��� queries ...
07:40:50 [firefox 47 #1m]
07:40:50 [firefox 47 #1m]       and the ...
07:40:50 [firefox 47 #1m]           ��� opens ...
07:40:50 [firefox 47 #1m]           ��� queries ...
07:40:50 [firefox 47 #1m]
07:40:50 [firefox 47 #1m]  ...
07:40:50 [firefox 47 #1m]
07:40:50 [firefox 47 #1m] 9 passing (1m, 36s)
07:40:50 [firefox 47 #1m]
07:40:50 
07:40:51 Trace: 9/30/2016, 7:40:51 AM Test Runner ERROR: 'Unhandled promise rejection in test runner child process, error: TypeError: [object Object] is not iterable!, promise: { state: \'rejected\',\n  reason: { [TypeError: [object Object] is not iterable!] screenshot: null } }.'
07:40:51     at logAtLevel (/home/jenkins/workspace/...)
07:40:51     at _failure (/home/jenkins/workspace/...)
...
07:40:51     at process._tickDomainCallback (internal/process/next_tick.js:122:9)
07:40:57 ------------------------------------------------------------------
07:40:57 [chrome #0p] Session ID: 21c1f339c0114eb985ebf895a16d98b9
07:40:57 [chrome #0p] Spec: /home/jenkins/workspace/.../isp.spec.js
07:40:57 [chrome #0p] Running: chrome
07:40:57 [chrome #0p]
07:40:57 [chrome #0p]   Can load the ...
07:40:57 [chrome #0p]       ��� contains an empty but fully ...
07:40:57 [chrome #0p]
07:40:57 [chrome #0p]
07:40:57 [chrome #0p] 1 passing (16s)
07:40:57 [chrome #0p]

In this case, the unhandled promise is not related to the test output either before or after it's position in the logs. In fact, I can't tell anything about what it maps to.

(Please see a PR for the wdio-jasmine-framework and the coherent reporter for some work implementing this.)