Use java.nio for all file operations

[nterry]

This would allow for alternate Filesystem implementations to be used such as JimFS and such for unit tests.

[FarooqKhan]

I had not realised this, I will try to check this out and fix it when i get some time.

[nterry]

@FarooqKhan Yeah man, check out JimFS here: https://github.com/google/jimfs

It would allow users such as myself to unit test without having to mock. You could have a constructor accept a java.nio.FileSystem object and default to the default filesystem.