Update dependencies for jupyter framework

[kevin-bates]

The dependencies upon lower level jupyter components have gotten to a point that they can be problematic for those installing kernel gateway on top of older versions. This issue can occur when older versions of jupyter_core (< 4.4.0) are present while updates to jupyter_client have occurred.

Since both Notebook (below) and Enterprise Gateway (above) are using updated dependencies, we should probably do the same for Kernel Gateway. The updates would include jupyter_core(>=4.4.0), jupyter_client(>=5.2.0) and notebook (>=5.3.0,<6.0)