(FACT-163) refactor fact [file] loading

This patch simplifies the logic for locating and loading fact .rb files.  It
reduces the search space for a fact files to only the configured search dir
paths (non-recursively).
Merge pull request #578 from jhoblitt/fact_loading

(FACT-163) refactor fact [file] loading
Merge branch 'stable' into facter-2
(fact-163) Remove relative path for FACTERLIB paths (which was unintentional)
Merge pull request #583 from kylog/issue/fact-163/fix-up-windows-specs

(fact-163) Remove relative path for FACTERLIB paths (which was unintenti...
(fact-163) Fix path construction in load_all
Merge branch 'facter-2'

Conflicts:
	lib/facter/util/loader.rb
	spec/unit/util/loader_spec.rb