use Counters as partial value to simplify HadoopCountersAggregator
Merge branch 'yingyi/fullstack_fix' into wbiesing/cleanup-statistics-aggregators
use pregelix CounterAggregator for vertex compute statistics
remove conflict in comments
Merge pull request #76 from uci-cbcl/wbiesing/cleanup-statistics-aggregators

cleanup statistics aggregators
Merge pull request #79 from uci-cbcl/wbiesing/fullstack_fix-pregelix-api-modifications-change-states-iteration-reporter-counters

Wbiesing/fullstack fix pregelix api modifications change states iteration reporter counters