Update lib/facter/version.rb for 1.6.18-rc1

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Merge branch '1.6.x' into 1.7.x

* 1.6.x:
  Update lib/facter/version.rb for 1.6.18-rc1
Merge branch '1.7.x'

* 1.7.x:
  Update lib/facter/version.rb for 1.6.18-rc1

Conflicts:
	lib/facter/version.rb