Update README.md and contributing.md (#78)

Signed-off-by: Anatoly Myachev <[email protected]>

Author: anmyachev

README.md

@@ -4,10 +4,10 @@
 
 # Dataframe API Compat
 
-Extremely lightweight compatibility layer between pandas, Polars, and any other project which implements the [Python Dataframe API Standard](https://data-apis.org/dataframe-api/).
+Extremely lightweight compatibility layer between pandas, Polars, Modin and any other project which implements the [Python Dataframe API Standard](https://data-apis.org/dataframe-api/).
 
 - ✅ No dependencies.
-- ✅ Lightweight: wheel is smaller than 30 kB.
+- ✅ Lightweight: wheel is smaller than 50 kB.
 - ✅ Simple, minimal, and predictable.
 
 Documentation, including installation instructions and tutorial, are here: https://data-apis.org/dataframe-api-compat.

contributing.md

@@ -9,10 +9,17 @@ pip install -r requirements-dev.txt
 Testing
 -------
 ```
-pytest test_standard.py --cov=dataframe_api_compat --cov=test_standard --cov-fail-under=100
+pytest tests --cov=dataframe_api_compat/pandas_standard --cov-fail-under=100 --library pandas-numpy
+pytest tests --cov=dataframe_api_compat/pandas_standard --cov-fail-under=100 --library pandas-nullable
+pytest tests --cov=dataframe_api_compat/polars_standard --cov-fail-under=100 --library polars-lazy
+# prerequisite: `pip install -r requirements-dev-modin.txt`
+pytest tests --cov=dataframe_api_compat/modin_standard --cov-fail-under=100 --library modin
 ```
 100% branch coverage isn't the objective - it's the bare minimum.
 
+**Note**: there is also requirement about 100% coverage in `tests` folder, however, to achieve one
+need to combine coverage from different implementations. How this is done can be seen in the `tox.yml` CI flow.
+
 Linting
 -------
 ```
@@ -25,11 +32,13 @@ Type Checking
 First, clone the [dataframe_standard](https://github.com/data-apis/dataframe-api) to some
 local path. Then, run:
 ```console
-MYPYPATH=<path to dataframe-api/spec/API_specification> mypy dataframe_api_compat
-MYPYPATH=<path to dataframe-api/spec/API_specification> mypy polars_standard.py
+MYPYPATH=<path to dataframe-api/spec/API_specification> mypy dataframe_api_compat/pandas_standard dataframe_api_compat/polars_standard
+# prerequisite: `pip install -r requirements-dev-modin.txt`
+MYPYPATH=<path to dataframe-api/spec/API_specification> mypy dataframe_api_compat/modin_standard
 ```
 
 For example, if you cloned both repos in the same place, this could be:
 ```console
-MYPYPATH=../dataframe-api/spec/API_specification/ mypy dataframe_api_compat
+MYPYPATH=../dataframe-api/spec/API_specification/ mypy dataframe_api_compat/pandas_standard dataframe_api_compat/polars_standard
+MYPYPATH=../dataframe-api/spec/API_specification/ mypy dataframe_api_compat/modin_standard
 ```