Apply filter to newly created files

This applies the filter function to new files. 

Currently the filter is only applied on the initial walk. This causes filtered-out files to be watched after they're edited at least once.

For example, I have a filtered-out file called "built.js" with compiled javascript. When I fs.writeFile to built.js, it's detected as a new file and is watched from that point forward.

Thoughts on this?