* Updated packages for Looker 21.20

* fix: codgegen for python had a parameter called 'models' but also a variable called 'models'. The names interfered. Aliased the models namespace to mdls in methods.py.

* docs: added note about linting to README

* fix: alias models namespace to mdls so no conflict with parameter models

* fix: look.id is now a string but tests were checking for integer

* fix: fixed minor changes to specs

* fix: add sdk-codegen/src tests into the mix