Fix PyO3 0.21 deprecation warnings

[kylecarow]

Also add rasterio and gdal imports at the top of the OSM example notebook to fail faster (rather than waiting for grade data to download on slow PyCon wifi)

https://pyo3.rs/v0.21.2/migration#from-020-to-021

According to the above link, there are some API changes for 0.21 to remove GIL markers. This means changing the pymodule def:

#[pymodule]
- fn routee_compass_py(_py: Python, m: &PyModule) -> PyResult<()> {
+ fn routee_compass_py(m: &Bound<'_, PyModule>) -> PyResult<()> {

As well as classmethod defs (though this one could be a staticmethod and it works just fine, since we don't use the pyclass):

- #[classmethod]
- pub fn _from_config_toml_string(
-     _cls: &PyType,
-     config_string: String,
-     original_file_path: String,
- ) -> PyResult<#name> {
+ #[staticmethod]
+ pub fn _from_config_toml_string(
+     config_string: String,
+     original_file_path: String,
+ ) -> PyResult<#name> {

Also in the OSM example I had issues with failing imports during grade data building, so I added a try/except at the top to catch those errors sooner.

Fixes #167

[nreinicke]

Looks great, thanks for fixing!