Add SoftLayer_Tag support to Fog::Compute::Softlayer

Fix compute mocks. [Now with lifelike action!]

Implement compute tags: mocks and tests.
Implement Fog::Compute::Softlayer#tagged_with method.
Add Tags example docs.
Fix Typo.
Fix another documentation typo.
Fix bare_metal attribute for Fog::Compute::Softlayer when reading from the API so it's less of a hack.
Merge pull request #5 from softlayer/compute_tags

Add SoftLayer_Tag support to Fog::Compute::Softlayer