added some TestMetadatum tests and a data helper module

Hello Anand,

these are some of the spec changes that i made

* added a module to facade the data creation part
* added some tests to the test_metadatum_spec.rb

the compare_runs tests that you mentioned were already there. However with the DataHelper module I created I should be able to refactor these to make them more readable

Also I should be able to use the data model to write view specs for compare runs 

I will get started for these soon

thanks
Shrikat