efbytesref as of 20140629

LUCENE-5524

This closes #50

Update to recent trunk.
Implement Accountable in EliasFanoDocIdSet.

There is one nocommit for the test of Accountable.ramBytesUsed on EliasFanoDocIdSet: disabled the test inherited from BaseDocIdSetTestCase because it fails even though there is a reasonable implementation.
The question is how to make this test pass: reimplement it to fit the implementation of Accountable in EliasFanoDocIdSet, or improve the implementation in EliasFanoDocIdSet. I'm probably overlooking something here.