Pre-release branch

[apiology]

This contains:

1. Remove unused file #1122
2. Support intersection types #1119
3. Update build matrix for new RBS release #1102
4. [blocker] Less-rigorous assertions merging assignment attribute of parameter pins #1088
5. Document 'solargraph config' command in README #1078
6. Move Pin::Base#infer deprecation to assert system #1075
7. Allow solargraph version to be overridden for dev/test purposes #1069
8. Extract gemspec, bundle and dependency management into its own class #1067
9. Add regression specs #1066
10. Improve typechecking of generics #1012
11. Add assertions around method aliases, add fixes #951
12. At alpha typechecking level, warn on method calls off of nilable types #803