v0.4.0

This release contains:

• Development:
  • create Length, Force, Surface and Stress units
  • add module, reference_diameter, lewis_factor, face_width, elastic_modulus, tangential_force, bending_stress, contact_stress, tangential_force_is_computable, bending_stress_is_computable, contact_stress_is_computable and mating_role properties to SpurGear
  • add compute_tangential_force, compute_bending_stress, compute_contact_stress methods to SpurGear
  • allow units absolute value computation
  • allow mating between gears only if they have the same module
  • update Solver to compute forces and stresses
  • update Transmission.snapshot and Transmission.plot to deal with new forces and stresses time variables
• Tests:
  • add tests for new units Length, Force, Surface and Stress
  • update SpurGear tests according to new properties and methods
  • update Transmission tests
  • update Solver tests
  • update utils tests
• Enhancement:
  • move general units operators to abstract base class
• Documentation:
  • fix installation documentation link
  • update dependencies documentation
  • fix docstrings vocabulary
  • add documentation pages for new SpurGear properties and methods
  • update first usage example
  • add second usage example
• Releasing:
  • move dependencies in specific separate files
  • update dependencies