corrected HITS calculation (issue gephi/gephi#620)

- initialized authority and hubs to 1 at each iteration
- used outgoing edges instead of incoming edges for hubs computation
- renamed 'target' to source for incoming edges in authority computation
- did not find anything wrong with authority calculation (this was questioned in the forum)

Validation of the logic would be appreciated.

Normalization is different from the one in the original research paper, but this might not be affecting the logic. networkx uses same normalization logic as the one used here.