(CFACT-44) Add missing Facter.version method.

Adding a missing Facter.version method that returns
Facter::FACTERVERSION.
(CFACT-44) Support boolean values in confines.

Support true and false in a Ruby confine hash.
(CFACT-44) Implement exec and which on Facter::Util::Resolution.

Implementing exec and which singleton methods on
Facter::Util::Resolution.

These call directly into the corresponding methods on Facter::Core::Execution.
(maint) Remove incorrect doc comment in #ifdef'd code.

Removing extraneous template argument doc comment.
Merge pull request #86 from peterhuene/custom/facts

(CFACT-44) More fixes for Ruby compatibility.