Remove redundant code in aloha.io package

[deaktator]

I think this is best done by removing com.eharmony.aloha.io.fs._ and placing any necessary functionality in com.eharmony.aloha.io.vfs. This is for a few reasons.

1. aloha-vw-jni and aloha-h2o use com.eharmony.aloha.io.vfs
2. com.eharmony.aloha.io.fs stupidly has the sealed trait FsInstance inside a package object. Since the classes are inner classes of the class package in the package com.eharmony.aloha.io.fs, the code can't (or at least can't easily) be used in Java.

Other classes in aloha.io use the aloha.io.fs package. This is especially true of aloha.io.sources._. These would have to be retrofitted to work with the aloha.io.vfs code.

This is a semantic versioning major version number bump and should be done as part of aloha 5.x.