New up-to-date notebook on ODEs (from prev work) (#478)

* New notebook on ODEs drawing from the previously scatter work and updating based on the current state of the pymc examples

* Revision #1 ODE Notebook based on Pymcdev comments

* Revision #2 ODE Notebook changes based on comments

* Revision #3 based on comments

* Revision #5 based on comments

Author: gbrunkhorst