Add error message to ArgumentError when adding a new item to a loader and the keys 'id' and 'term' are not defined.
Change language for the error message in the Loader class when adding an item without the 'id' and 'term' keys.
Merge pull request #42 from dagosi89/master

Add error message to ArgumentError when adding a new item to a loader and the keys 'id' and 'term' are not defined.