new fact: lvm_support, and related rspec test suite
Fix some things as per @adrienthebo's comments:

  * Put Facter::Util::Resolution.exec inside setcode block when
    possible
  * Use true/nil instead of yes/no
  * Use each_with_index
  * Move doc before each fact declaration
Merge pull request #25 from raphink/up_lvm_support_fact

Add lvm_support fact