Error handling and management

[snkas]

While testing, I was really struggeling with the question 'To what extent should this API be demanding/defensive?'

Currently (in my fork) the Comments/Submissions/Subreddits classes have minimal preconditions for the arguments, with only throwing a IllegalArgumentException if one of the arguments is totally invalid (like a null when retrieval submissions of a subreddit).

But for example you receive a 403 when trying to retrieve submissions, should this result in a null, an empty list of submissions or an exception PermissionDeniedException? And should these be Runtime or Static exceptions? Any thoughts guys? @karan ?