Optimizely-sdk

Bug Fixes:
* Fixed handling of network and no status code errors when polling for datafile in `PollingConfigManager` and `AuthDatafilePollingConfigManager`. ([287](https://github.com/optimizely/python-sdk/pull/287))

Bug Fixes:
* Fixed HTTP request exception handling in `PollingConfigManager`. ([285](https://github.com/optimizely/python-sdk/pull/285))

New Features:
* Introduced 2 APIs to interact with feature variables:
* `get_feature_variable_json` allows you to get value for JSON variables related to a feature.
* `get_all_feature_variables` gets values for all variables under a feature.
* Added support for fetching authenticated datafiles. `AuthDatafilePollingConfigManager` is a new config manager that allows you to poll for a datafile belonging to a secure environment. You can create a client by setting the `datafile_access_token`.

Bug Fixes:
* Fixed log messages for targeted rollouts evaluation. ([268](https://github.com/optimizely/python-sdk/pull/268))

Bug Fixes:
* Adjusted log level for audience evaluation logs. ([267](https://github.com/optimizely/python-sdk/pull/267)).

Bug Fixes:
* Updated `jsonschema` to address [installation issue](https://github.com/optimizely/python-sdk/issues/232).

New Features:
* Added a new API to get project configuration static data.
* Call `get_optimizely_config()` to get a snapshot of project configuration static data.
* It returns an `OptimizelyConfig` instance which includes a datafile revision number, all experiments, and feature flags mapped by their key values.
* Added caching for `get_optimizely_config()` - `OptimizelyConfig` object will be cached and reused for the lifetime of the datafile.
* For details, refer to our documentation page: [https://docs.developers.optimizely.com/full-stack/docs/optimizelyconfig-python](https://docs.developers.optimizely.com/full-stack/docs/optimizelyconfig-python).