pip install -e is broken

[pgunn]

The -e install doesn't put paths in the right place for caimanmanager to find them, looking in paths like:
/home/pgunn/miniconda3/envs/caibuild/share/caiman

We need to handle this case better.

[pgunn]

It's unclear whether this is because the install plumbing is bad or caimanmanager needs to be smarter. Probably the former though. This may have happened when we modernised the pip plumbing a few releases back, as I know this used to work.

[pgunn]

Actually, caimanmanager install --inplace does the right thing with an editable install, but only if you do it from within the sourcedir.

I may be able to find a more elegant way to do this (maybe caimanmanager should detect if the install is editable and then go find the sourcedir) and then I wouldn't need the flag, but if not, I at least need to document editable installs better in the readme.

[pgunn]

Looks like the data_files limitation is a known bug in setuptools:
pypa/setuptools#3399

Currently looking into whether there's any way to force setup.py to populate share/ with our data_files anyway or if there's any way to disable editable mode; either approach seems workable.

[pgunn]

Should be fixed by #1357