Fix usage of zip for Ruby 2.0

* In Ruby 2.0 it does not automatically coerce arguments to an
  Array, so it needs to be done manually, which is good since the
  resulting code is nicer anyway.
Fix ci task to run spec task

* The metrics:all task was removed earlier.
Remove rcov gem dependency
Upgrade yard and yardstick gem dependencies
Update yardstick threshold to match current coverage
Update addressable gem dependency to specify minimum version
Add #adapter and #repository methods to adapter shared specs