readme: improved apis

Matrix.get(), Matirx.add(), and Matrix.sub()
gyp: enable RTTI and Exception for win
src: added 'Matrix.mul()' and 'Matrix.mula()'

change the name of private member function from
is_nonconformate_argument to is_nonconformate_arguments
test: add 'Matrix.mul()' and 'Matrix.mula()' testing

update ‘Matrix.adda()’ and ‘Matrix.suba()’ testing
readme: added 'Matrix.mul()' api