mahoro 0.4 - documentation updates and concurrency

All public API methods are now documented, using "ri" documentation
(built during the RubyGems install) is recommended for users.
Plain-text API documentation is also available online:
http://bogomips.org/mahoro/API

On Ruby 1.9 and 2.0, Mahoro now releases the GVL for all operations
which may touch the filesystem.  This allows several threads with
thread-local Mahoro objects to simultaneously work on multiple files at
once.

Since libmagic is not thread-safe, neither is Mahoro (by default).  An
optional Mahoro::ThreadSafe module now exists for applications which may
spawn many short-lived threads.  Applications using long-lived threads
and needing real concurrency should use thread-local Mahoro objects
instead of the ThreadSafe module.

Eric Wong (10):
      INSTALL: improve documentation for deb/rpm-based distros
      gemspec: cleanup and update rdoc options
      add RDoc documentation
      test: be more flexible with Mahoro::NONE matches
      release GVL if filesystem I/O is required
      Mahoro#file supports objects with #to_path support
      split out nogvl_compat header
      cleanup: make cMahoro an automatic variable
      add optional thread-safety module
      tree reorganization + various maint fixes