Handle-based entity management in C++11/C++14

"If I want to store entities contiguously to improve efficiency, how can I keep track of them?"

In the video, I show two possible ways of dealing with entity storage and management:

Storing entities on the heap. Entities are easy to keep track of, but iteration is inefficient. Very easy implementation.
Storing entities contiguously. Iteration is cache-friendly, however it is hard to keep track of specific instances. Complex implementation with custom handles.

Hope you find some of the concepts in the video interesting!
I'm looking forward to your feedback and to more ideas on entity management.