add lgtm integration

[wholmgren]

https://lgtm.com/projects/g/SolarArbiter/solarforecastarbiter-core/overview/

also enabled pull request review integration in github organization settings

[lboeman]

Looks like LGTM is producing alerts for versioneer, is that to be expected? I don't quite grasp what path_classifiers is doing and a quick look through their documentation doesn't show anything about excluding files.

[wholmgren]

Thanks for checking. Looks like their yaml spec has changed since I first did this in pvlib/pvlib-python#561

[wholmgren]

here's their documentation: https://help.semmle.com/lgtm-enterprise/user/help/lgtm.yml-configuration-file.html

[lboeman]

Thanks for checking. Looks like their yaml spec has changed since I first did this in pvlib/pvlib-python#561

It looks like the .lgtm.yml is written correctly, and the pvlib version isn't suffering from the same issue. The only difference I can see is the lack of newline at the end of the .yml file which perhaps is affecting parsing?

[wholmgren]

generated is a valid tag: https://help.semmle.com/lgtm-enterprise/user/help/file-classification.html#built-in-tags

I think LGTM config must be in the head master, not the merge candidate. Tony's not here, so let's merge it and find out!