Implementation for issue-38: ATE student UI update

Implementation for issue #38 

This PR updates the automated test student interface to match the layout in our specification and properly utilize the updated TestScript and TestScriptResult models.

![screen shot 2013-12-18 at 9 01 54 pm](https://f.cloud.github.com/assets/919790/1779666/9aa5f7a6-6851-11e3-9e0c-b106bca554cd.png)

Changes:
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* Remove use of old display settings attributes on the TestScript models
* Create a TestRunResult model that provides an abstraction of a TestRun and create a one to many relationship between a TestRunResult and TestScriptResults.
* Update layout UI to match specification and use the new TestRunResult model
* Add unit testing for the new TestRunResult model

NOTE: This PR includes a database migration. After the merge you must run:

    bundle exec rake db:migrate