Updates API call 

When using the SDK and consulting this example app, one thing I found really confusing was how to properly construct the API call. I think this is in part due to the fact that there's a lot of similarity to the table name and the columns being queried. 

In light of completely changing the example, I clarified how the call is formed, with the location of the dataset followed by the table name. I also added a link to the dataset being used. 
I also cleaned up the file a bit, deleting some of the extra white space. 

:sparkling_heart: 

ETA: Another thing that contributes to this confusion is that the documentation linked to from the [official developer page](http://developer.dol.gov/sdk-documentation/ruby-federal-data-sdk) page is not the same as what's included in the [documentation branch of this repository](https://github.com/USDepartmentofLabor/Ruby-Sample-App/tree/gh-pages). I'd recommend updating the to reflect what's in this repository, as it is more complete.