Launchdarkly-server-sdk

Changed:
- To reduce the network bandwidth used for analytics events, feature request events are now sent as counters rather than individual events, and user details are now sent only at intervals rather than in each event. These behaviors can be modified through the LaunchDarkly UI and with the new configuration option `inline_users_in_events`.
- The analytics event processor now flushes events at a configurable interval defaulting to 5 seconds, like the other SDKs (previously it flushed if no events had been posted for 5 seconds, or if events exceeded a configurable number). This interval is set by the new `Config` property `flush_interval`.

Removed:
- Python 2.6 is no longer supported.
- Removed the `Config` property `events_upload_max_batch_size`, which is no longer relevant in the new event flushing logic (see above).

Fixed
- It was not possible to install the SDK with `pip` 10.0.0. This should work now (thanks, [theholy7](https://github.com/launchdarkly/python-client/pull/82)!) with the latest `pip` as well as previous versions.

Fixed
- Fixed a bug that, in Python 3.x, caused an error when using an integer user attribute to compute a rollout.
- Fixed a bug that, in Python 3.x, made the `all_flags` method return a dictionary with byte-string keys instead of string keys when using the Redis feature store.

Fixed
- In the Redis feature store, fixed a synchronization problem that could cause a feature flag update to be missed if several of them happened in rapid succession.

Added
- Support for a new LaunchDarkly feature: reusable user segments.

Changed
- The `FeatureStore` interface has been changed to support user segment data as well as feature flags. Existing code that uses `InMemoryFeatureStore` or `RedisFeatureStore` should work as before, but custom feature store implementations will need to be updated.

Removed
- Twisted is no longer supported.

_This release was broken and has been removed._