Combine attr declarations
Decouple Resource from SoftwareSpec
SoftwareSpec tests are now Resource tests
Reimplement SoftwareSpec on top of Resource
Move formula resources to SoftwareSpec
Track initialized specs
Make top-level resources apply to all specs
Make spec-scoped resources override top-level resources
Download strategies take a resource now
Reorganize resource download methods
More useful error message for missing checksums
scala: use resources
git-flow: use resources
git-flow-avh: use resources