Add nbconvert script to make the example files into .py files

[tms-bananaquit]

Fixes #64 . Adds docs/source/examples/convert_notebooks.py to convert the notebooks to .py scripts in the right directory.

The intent for this one is just to add a script that converts everything in /docs/source/examples into .py files in /examples/, so that we don't have to do double-maintenance on them, as has already come up in the last two PRs.

• Resolve the RTD issue
• Markdown cells get thrown out. Can we include an nbconvert preprocessor s.t. the raw markdown is included as comments?
  • Nope.

[tms-bananaquit]

I added a function that finds the location of the Circle data for the examples, to resolve the problem where the notebooks' and the .py files' relative directories differ. This is done by finding the root of the git repo, so it works fine locally, since that's where I run out of -- but of course that fails on RTD, when nbsphinx tries to do the conversion out of its temporary directory:

FileNotFoundError: [Errno 2] No such file or directory: '/home/docs/checkouts/readthedocs.org/user_builds/menelaus/checkouts/64-nbconvert-scripts/docs/source/examples/change_detection/src/menelaus/datasets/dataCircleGSev3Sp3Train.csv'

@Anmol-Srivastava Did you ever resolve the bit with the absolute paths before we switched away from it as a solution?

[tms-bananaquit]

I don't think this is going to work until we get a version of the streaming data that's generated live, rather than read from a file.

Of course, we had it working on dev, so I could implement a hideous switch statement that just tries the paths that we actually use until one of them exists. This is not a good solution, but we can use it in the meantime to avoid having to make these tweaks repeatedly in two places.

As it turns out, my original solution did work, but for a fatfingering of the syntax. Switching back resolves the local stuff and RTD. 🙃

[Anmol-Srivastava]

Minor optional comments, and one point about the find_git_root location.

[Anmol-Srivastava]

One last thing, I think _locate also ended up in /src/menelaus somehow on top of being in utils