More explanatory errors matching Java client

[zeynepsu]

There are no exceptions thrown if the user is doing Algorithmia.file().get on someone else's collection, or a non-existent collection. Then, let's say I tried to retrive a Json from a file in the data api and get the field "acces_key". The error I get when I run this code is: "Error: 'access_key'". This does not help me debug what went wrong at all.