chore(example): remove source files from files/preprocessors
chore(example): remove source files from files/preprocessors

Right now this is officially incorrect/unsupported
so using it in tthe example is confusing. Even when #52
can be solved it's easier to just be consistent (tests only)

Closes #55, Reverts c9d9d78896db0cd443c0182e32214d23768f67aa

pmowrer/karma-browserify,Nikku/karma-browserify,sdtsui/karma-browserify