v0.3.3 - Keying and Onion Skin improved

• The addon will now assert that the active object should be of MESH
  type. If not, the appropriate operators will be inactive

• Fixed issue that artists were not able to override keyed value in an
  existing keyframe

• Fixed #9 that the Initialize Frame Handler had to be manually
  invoked by artists periodically to avoid issues. This has been fixed
  by calling the frame handler every 180 seconds, and also after a file
  is loaded

• The panel will now display a warning if there are no active objects
  and also when the active object is not of MESH type

• The active object's validity is now checked properly for all operators
  that depends on it.

• Fixed issue that incorrect number of poses were displayed for the future variant for Onion Skin

• Fixed issue that if the operators were invoked when the active object is None, it would throw errors