MrTheodor's dataFilter (proposed)

@MrTheodor you guys gotta remember to open pull requests if you want us to merge in / review your code :)

**My notes:**

* Remove the word 'filter' from the module name since it's already in the folder (and is implied)
* In fact, drop the name 'data' altogether and use something more concise such as 'extract' or 'subset'
* This seems similar to a filter I proposed earlier called 'extract' which behaves in a similar manner to that of _.js pluck() method.