Ipykernel

- Restore timer based event loop as a Windows-compatible fallback.
[523](https://github.com/ipython/ipykernel/pull/523)

- Fix 520: run post_execute and post_run_cell on async cells
[521](https://github.com/ipython/ipykernel/pull/521)
- Fix exception causes in zmqshell.py [516](https://github.com/ipython/ipykernel/pull/516)
- Make pdb on Windows interruptible [490](https://github.com/ipython/ipykernel/pull/490)

5.3.0 Adds support for Trio event loops and has some bug fixes.

- Fix ipython display imports [509](https://github.com/ipython/ipykernel/pull/509)
- Skip test_unc_paths if OS is not Windows [507](https://github.com/ipython/ipykernel/pull/507)
- Allow interrupting input() on Windows, as part of effort to make pdb
interruptible [498](https://github.com/ipython/ipykernel/pull/498)
- Add Trio Loop [479](https://github.com/ipython/ipykernel/pull/479)
- Flush from process even without newline [478](https://github.com/ipython/ipykernel/pull/478)

- Handle system commands that use UNC paths on Windows
[500](https://github.com/ipython/ipykernel/pull/500)
- Add offset argument to seek in io test [496](https://github.com/ipython/ipykernel/pull/496)