Incompatible with Pyramid 1.10 due to removal of set_request_property

[Deimos]

Pyramid 1.10 has removed the pyramid.config.Configurator.set_request_property method (which has been deprecated since 1.5): https://docs.pylonsproject.org/projects/pyramid/en/latest/whatsnew-1.10.html#backward-incompatibilities

pyramid_webassets uses this, so it currently crashes when used with Pyramid 1.10:

pyramid_webassets/pyramid_webassets/__init__.py

Lines 396 to 398 in 4109bba

	config.set_request_property(get_webassets_env_from_request,
	'webassets_env', reify=True)
	config.set_request_property(assets, 'webassets', reify=True)

[tilgovi]

Would you make a PR replacing it with add_request_method, please? We can then make sure all the tests pass and release a 0.10 version.

[tilgovi]

Also, please bump the Pyramid requirement in setup.py to pyramid >= 1.4.

[Deimos]

Sure, I can do the PR if someone can do a release for it. Thanks.

[tilgovi]

Closed by #66 and released as v0.10. Thanks, @Deimos!