Launchdarkly-server-sdk

Fixed
- [65](https://github.com/launchdarkly/python-client/issues/65) Ensure that no warning is logged about a missing SDK key when the `ldclient` package is imported.

Changed
- Fixed missing python2.6-requirements.txt in manifest

Added
- Support for Python 2.6.

Changed
- RedisFeatureStore now returns default when Redis errors occur
- Better detection of stream connection issues.

Changed
- Changing the config and SDK key is now supported after initialization. The client will be restarted with the new configuration
- Breaking api change: `ldclient.sdk_key = <KEY>` replaced with: `ldclient.set_sdk_key('<KEY>')`
- Breaking api change: `ldclient.config = config` replaced with: `ldclient.set_config(config)`
- No longer depend on sseclient library, instead include our own sse client

Changed
- Add backoff when retrying stream connection.
- More correct initialized state.