Adding support for ICE

Summary of additions:

- added `guard`
- created `bin/damage.thor` to easily test connectivity.  See https://github.com/wearemolecule/damage/issues/1 for some follow-on thoughts.
- moved bulk of `Damage::Client` to a module, `Damage::Client::Base`
- add logging configuration to allow connecting to client systems, a la:

  ```ruby
  Damage.configuration.logger = Rails.logger
  ```

- added some validation checks in `Damage::Message`
- finished `Damage::Persistence::FilePersistence` (or at least made it functional)
- added meta methods to `Damage::Schema`.  Also added support for non-library-included schema definitions
- added FIX 4.4 support
- added ability to customize the `Damage::Client` via a vendor param (to support ICE)