better loadNpmTask injection

I managed to add string arrays as an input for loadNpmTask; I also modified the existing test and README
It create a new array without duplicates; the test pass and the element is added to the new array if I can find it first when I search for it in the sorted array.

The condition `array.indexOf(el) === index` return true only if the first element *el* found in the input array is the one we are currently testing.
 
http://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter