adds basic intro to readme
BC: changes Rjson structure by adding opening bracket to file
version bump
adds distinguishing between array and object buffer types
changes KeyValueStore physical buffer to array
fixes buffer type checking in Rjson.write()
consolidates file system callback methods
fixes compaction handler in Rjson
makes KeyValueStore buffer consolidation self-consistent, so compaction would work
shortens `key` and `value` in KeyValueStore to `k` and `v` respectively
updates readme for 0.2.0 features