Feature: custom Hoya home

This feature adds a configuration option for setting the Hoya base directory in HDFS. By default, this is `/user/<shortname>/.hoya`.

We extracted static methods from `HoyaUtils` that  manipulated `FileSystem` objects into a new class, `HoyaFileSystem`. This object encapsulates both configuration state and file system behavior. This way, clients calling `getBaseHoyaPath` on a `HoyaFileSystem` object are returned a `Path` that can be controlled by configuration.

This branch has been rebased on top of the latest 0.11.1 release, and the tests pass.