upgrade version (#54)

* upgrade version

* fix

* fix doc

* fix notebooks

* vers

* doc

* fix notebook

* fix

Better mathematical expression (#52)

* Improve style

* fix ext

* fix ut

* ext

* fix

* req

* remove

* req

* fix ut

* fix paths

* Replace \R by \mathbb{R}

* urls

* nb

* using github only

* fix ut

a bug to find