updated Observe tab's topic bar
Major refactor, including:
1. Moved to a complete asynchronous request/response cycle for all HTTP requests.
2. Redesigning the Observe/Consumers tab
3. Minor clean up.
improved readability and type-safety
continued refinement and clean up
performance optimizations and removal of redundant code
fixed streaming consumer update issues
fixed issue with negative deltas
bumped the revision to 0.18.9
Merge branch 'feature/webui' into scala_2.11

* feature/webui:
  bumped the revision to 0.18.9
  fixed issue with negative deltas
  fixed streaming consumer update issues
  performance optimizations and removal of redundant code
  continued refinement and clean up
  improved readability and type-safety
  Major refactor, including: 1. Moved to a complete asynchronous request/response cycle for all HTTP requests. 2. Redesigning the Observe/Consumers tab 3. Minor clean up.
  updated Observe tab's topic bar