Unit testing and performance suggestions

I forked your code and added a stub unit test based on the template I showed you before.

There are comments in the code with some thoughts for you to consider. The bulk are in list_t.hpp with some more in node_t.hpp and their respective unit tests. The unit tests are incomplete. If you continue with this example, try writing a test that exercises your anticipated interface with a stub function for that interface. Get it to compile but fail to pass because the EQ or other assertions are not met. Then, implement the feature until all tests pass. (TDD)

This is my first pull request but I take it that you will be given an option to accept it and you'll get the patch with my changes. Let's see how it works.