Modified OutputBuffer to have an error function to output to stderr

[FlyingPhish]

Added error function to OutputBuffer to output errors to stderr, then changed a bunch of .fails where the values were error: or [exception].

Have tested and code appears to work as intended.

[jtesta]

@FlyingPhish : I provided feedback on some of your proposed changes. Looks good otherwise.

[jtesta]

@FlyingPhish: if you're able to make the minor changes I requested in the review, and resolve the merge conflict, I can go ahead and merge this. Thanks!