Add :logs to build model

[skierkowski]

The current Build model doesn't include a :logs attribute. This bug is to add a few things...

• Add :logs attribute, an Array of Strings to the model
• Add an API at /builds/:id/logs which supports GET, POST, and PUT
  • GET gets the list of all the logs, an array of strings
  • POST allows posting a single string which appends a log to the logs array
  • PUT takes an array of strings and can be used to update all of the logs at once
• The Builds API Resource (Ephemeral::Resources::Build) should be updated to not return the logs

[skierkowski]

I should have clarified this issue a bit more. I am re-opening this and adding more details in the description.