Upgrade node-block-queue to v0.0.2
Keep ordering on each single connection;
db#del is also mapeable
Roll back connection pool for db#client
Add bench result for 100op 500op 1000op 5000op
v0.0.4
Merge branch 'dev'

* dev:
  v0.0.4
  Add bench result for 100op 500op 1000op 5000op
  Roll back connection pool for db#client
  db#del is also mapeable
  Keep ordering on each single connection;
  Upgrade node-block-queue to v0.0.2