Remove workaround for Issue 122
Clean up BallJoint and FreeJoint
Add a test for Issue 122
Fix typo
Merge branch 'origin/master'
Improve integration for BallJoint and FreeJoint
Merge branch 'origin/master'
Fix setting joint rest position in testDynamics.cpp
Fix typo and add comment on Integrator
Rename Integrator::evalAccs() to Integrator::evalGenAccs()
and add some comment on World
Restore RK4 integrator with updated integration api
Add SemiImplicitEulerIntegrator
Reduce number of virtual functions for Integrator
Update testJoints.cpp for BallJoint and FreeJoint
Don't integrate for immobile skeletons
Update Migration.md and rename FreeJoint mR to mQ
Update Changelog.md
Fix typo in Changelog.md
Merge pull request #168 from dartsim/issue122

Fix incorrect integration of BallJoint and FreeJoint using modified integration API