adds models.user.yml to .gitignore

[jakenvac]

I thought this might be useful for people who like to test out others branches etc. and hate having to make sure their config doesn't end up with conflicts or being outright overwritten.

[lstein]

Nice idea. I did the same thing for my config file but named it ls-models.yaml. The timing here is good, because I'm in the middle of writing the documentation for loading and editing new models, and I'll use your naming convention for this.

[jakenvac]

Thanks for merging and thanks for all your hard work on the project!