Latest SymPy Docs have changed various references

[moorepants]

/home/moorepants/Manuscripts/learn-multibody-dynamics/angular.rst:148: WARNING: external py:meth reference target not found: sympy.physics.vector.frame.ReferenceFrame.orient_explicit
/home/moorepants/Manuscripts/learn-multibody-dynamics/lagrange.rst:148: WARNING: external py:meth reference target not found: sympy.matrices.matrices.MatrixCalculus.jacobian
/home/moorepants/Manuscripts/learn-multibody-dynamics/mass.rst:742: WARNING: external py:func reference target not found: sympy.physics.mechanics.functions.inertia
/home/moorepants/Manuscripts/learn-multibody-dynamics/mass.rst:958: WARNING: external py:meth reference target not found: sympy.matrices.matrices.MatrixEigen.eigenvects
/home/moorepants/Manuscripts/learn-multibody-dynamics/orientation.rst:557: WARNING: external py:meth reference target not found: sympy.physics.vector.frame.ReferenceFrame.orient_explicit
/home/moorepants/Manuscripts/learn-multibody-dynamics/orientation.rst:589: WARNING: external py:meth reference target not found: sympy.physics.vector.frame.ReferenceFrame.orient_explicit
/home/moorepants/Manuscripts/learn-multibody-dynamics/orientation.rst:612: WARNING: external py:meth reference target not found: sympy.physics.vector.frame.ReferenceFrame.orient_explicit
/home/moorepants/Manuscripts/learn-multibody-dynamics/simulation.rst:288: WARNING: external py:func reference target not found: numpy.deg2rad
/home/moorepants/Manuscripts/learn-multibody-dynamics/simulation.rst:288: WARNING: external py:func reference target not found: numpy.rad2deg
/home/moorepants/Manuscripts/learn-multibody-dynamics/simulation.rst:812: WARNING: external py:meth reference target not found: sympy.matrices.common.MatrixCommon.row_join
/home/moorepants/Manuscripts/learn-multibody-dynamics/sympy.rst:726: WARNING: external py:meth reference target not found: sympy.matrices.matrices.MatrixCalculus.jacobian
/home/moorepants/Manuscripts/learn-multibody-dynamics/sympy.rst:870: WARNING: external py:meth reference target not found: sympy.matrices.matrices.MatrixBase.inv
/home/moorepants/Manuscripts/learn-multibody-dynamics/sympy.rst:877: WARNING: external py:meth reference target not found: sympy.matrices.matrices.MatrixBase.LUsolve
/home/moorepants/Manuscripts/learn-multibody-dynamics/sympy.rst:958: WARNING: external py:meth reference target not found: sympy.matrices.matrices.MatrixBase.LUsolve

This would't occur if SymPy hosted the old versions of the documentation and we could pin to the inv file for that specific version.