Release 0.5.0

[zhaijack]

Tracking the checklist for completing release 0.5.0

• [x] code refine
  • [X] Code cleanup for 0.5.0 release #166
• [x] Release Notes (feature highlights) #168
• [x] Documentation for new features #170

[sijie]

I linked #166 here - this issue is to clean up API code to make sure we have a clean API for 0.5.0 release.

[sijie]

assigned to @zhaijack since he is the release manager for 0.5.0

[zhaijack]

close it