refact all methods (keep native string interpolation)
change tab indentation to spaces, remove tests from main file
Fixing cases where "undefined" was printed instead of an error message

Turns out there are cases where an err will not have a stack, even though it should.
This catches that condition, and shows the message when stack is unavailable.
Merge pull request #3 from component/stack-undefined-fix

Fixing cases where "undefined" was printed instead of an error message
1.1.2
Merge branch 'refact/keep-log-interpolation'

Conflicts:
	index.js