Update CHANGELOG.md

Update CHANGELOG.md

Update setup.py

Move PostMesh to an external python package

clean ups for new tag

Fixed the factor bug in most electromechanics materials. Two equivale…

…nt models one with helmholtz and one with internal energy implemented for proof checks. 3D problems still behave strange, further tests required

Stress/secondary variables recovery completely implemented. Nonlinear…

… mechanics solver working

This is an immediate clean-up and release version for florence. Many …

…old features in Mesh class are now removed. Please revert to the previous version if any of those features are needed for debugging

major refactoring. All tri gauss quadrature rules are now read. Probl…

…ems renamed to Examples. imp imports are removed. More code clean ups

all solvers linear, linearised and non-linear working fine. A tag als…

…o created