Fix bug using 'exclude' without 'files' option

When using the 'exclude' option without also using the 'files' option
you get an error "Cannot call method 'push' of undefined". This is
because the merged array variable in only instantiated when newValue
(files option) is truthy.

Updated readme, Werner van Deventer and BrutalDev are the same guy :)
'exclude' ignored when not using 'files' option

When omitting the 'files' option, any 'exclude' options provided are also ignored.
Merge pull request #178 from brutaldev/master

Fix bug using 'exclude' without 'files' option