fix imports in example postmodeling notebook

[shaycrk]

Import postmodeling utilities from installed triage rather than assuming notebook is being run in postmodeling code directory for example notebook.

[codecov-io]

Codecov Report

Merging #646 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #646   +/-   ##
=======================================
  Coverage   82.98%   82.98%           
=======================================
  Files          87       87           
  Lines        5754     5754           
=======================================
  Hits         4775     4775           
  Misses        979      979

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8ceaf48...963462c. Read the comment docs.

[nanounanue]

Already fixed in dirty 🦆, but I see you point

[jesteria]

👍

[nanounanue]

We should clean this namespace and import from __init__.py ...