CoqHammer v1.3 tutorial

Tutorial videos are available [here](https://www.youtube.com/watch?v=0c_utk9bVgU&list=PLXXF_svQE_b8ux7fJTL-XX2yjUhYSkYcb).

The tutorial files should be read in the following order:

1. [sauto/isort.v](sauto/isort.v)

2. [sauto/isortb.v](sauto/isortb.v)

3. [sauto/itrev.v](sauto/itrev.v)

4. [sauto/order.v](sauto/order.v)

5. [sauto/msort.v](sauto/msort.v)

6. [sauto/imp.v](sauto/imp.v)

7. [sauto/exp.v](sauto/exp.v)

8. [hammer/demo.v](hammer/demo.v)

9. [hammer/gcd.v](hammer/gcd.v)

See also a formalisation of various sorting algorithms with `sauto`:
[https://github.com/lukaszcz/sortalgs](https://github.com/lukaszcz/sortalgs).
