Fix deleteJob function by ignoring the exception thrown when a node is already removed
Replace the test framework with Hspec
Add a multithread test
Take a lock for a sqlite3 session
Fix updateDBQueue of sqlite3 backend
Fix BackendQueue test
Version 0.0.17
  - Fix BackendQueue test
  - Fix updateDBQueue of sqlite3 backend
  - Take a lock for a sqlite3 session
  - Replace the test framework with Hspec
  - Fix deleteJob function by ignoring the exception thrown when a node is already removed