evaluate rep score replacement

[roadscape]

One way to approximate the current rep score is to sum of all of a user's posts net_rshares. Where this differs from follow plugin is that users with lower rep can bring down those with higher rep.

In the short term it may be ideal to keep it in steemd (see https://github.com/steemit/steem/issues/1425). Long term, we may want to implement some other algorithm entirely.