Switch missing build directory to an error
Switch missing build directory to an error

If the build directory doesn't exist it's likely user error. WE shouldn't
version nothing.

robwierzbowski/grunt-build-control,antyang/grunt-build-control,fiznool/grunt-build-control,antyang/grunt-build-control,fiznool/grunt-build-control,robwierzbowski/grunt-build-control