Merge pull request #8 from KnowSheet/review

Left only string key/value/pairs events.
Fixed Cereal’s polymorphic serialization.
Fixed compile error with message queue.
Moved Statistics Uploader mock to the separate header.
Removed temporary boolean.
Faster push to queue.
Initial compilable File Storage Queue
Fixed missing header guard in logger.
Removed unused tests.
Fixed duplicate scope guard.
Integrated file storage queue.
// @TODO simplify it.