SLEAP v1.0.10a4

Pre-release of minor version update with performance tweaks and bug fixes.

Changes:

• Update to TensorFlow 2.1.2 (security patch)
• Switch to ID-based hashing for LabeledFrame. This dramatically increases the performance of frame manipulation operations.
• Several convenience methods for sleap.Labels:
  • Add describe method to Labels for easy inspection of dataset stats
  • Add has_frame method to Labels for quick checking of frame existence
  • Add remove_user_instances and remove_predictions for quick dataset cleanup
• Remove predicted instances in existing frames before merging in active learning results (fixes #413)
• Conda environment.yml clean-up: de-duplicates dependencies managed by pip