Hadupils::Search functions for finding directories

One notion for Hadupils is that certain directories will be
searched for within the filesystem, starting at the present
working directory, so that they can be used to affect hadoop/hive
sessions.

Hadupils::Search provides functions for performing the filesystem
upwards walk:
* find_from_dir(name, start) will look for a directory with
  basename _name_, starting by looking *within* _start_.  Returns
  the absolute path of the directory if found; returns nil if not
  found.
* find_from_pwd(name) does exactly the same but uses the present
  working directory as the starting point.

Also eliminated the use of autoload in lib/hadupils