Release v0.4.0

• remove mkl-service dependency (fixes #24 and #26)
  • get_max_threads and set_num_threads methods are removed from the PyPardisoSolver class, use mkl-service directly if you require them
• change how the shared_library mkl_rt is detected to account for differences between conda and pip
  • also removes the psutil dependency

This is the last release with a manual changelog. The old CHANGELOG.md file can be viewed here.