Expose testem's CI reporter option to the ci-task. This allows you to
customize the spec-ci task with two new 'reporter' and 'reporterOutput' options
allowing you to change the output style and capture to a file.
Initial tweaking & refactoring of #249

Thanks to @gruntruk for the contribution
Pulls out the "write & acc stdout" stuff 

We seem to do this everywhere, so I yanked it.
reorganize spec-ci file a bit
Move logging about report up as a script guard

Surely somebody has a script looking for "OK" at
the end of the output, so let's not betray TAP by 
tacking on more output at the end
Express args as a series of array concats.

This looks a little cleaner to me.