Add automated performance tests

[mpareja]

• given an ASG with 3 instances running uncorded
  • add performance: measure how long it takes to add a document to a node
  • add throughput: measure how quickly we can add documents to the cluster
  • remove performance: measure how long it takes to remove a document from a node
  • remove throughput: measure how quickly we can remove documents from the cluster
  • replication latency: measure how long before each node received the last write
  • memory usage: measure memory growth as we add documents to the cluster
  • memory usage: measure memory growth as more peers connect and reconnect