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

Review of the logic would be appreciated.

Normalization is different from the one in the original paper, but this might not be affecting the logic. networkx uses same normalization logic as the one used here.
Merge pull request #756 from Mango-information-systems/fix-hits

corrected HITS calculation (issue gephi/gephi#620)