fix a bug. zeroObject() was called in releaseObject()
fix comile errors
fix compile errors
make destructor virtual and fix compiling errors with g++
Merge pull request #31 from norihiro-w/fix-gnu-build-errors

Fix gnu build errors
Merge pull request #32 from norihiro-w/Add_AdaptTimeSteping

support adaptive time steptting based on newton solver
fix a bug in accept(). it should check current time
Merge pull request #33 from norihiro-w/fix-timestep-vec

Fix a bug that time step was incorrectly updated when multiple time step function exists
adding a local _dt variable to store previous time step size.