* internal/data: move codec to own subpackage
* internal/data/codec: check & test nil Entry Decode
* internal/data/decoder: test for short prefix error
* internal/data/codec: test invalid key & value sizes
* internal/data/codec: check & test for truncated data
* interna/data/codec: use assert for tests
* internal/data: comment exported functions
* internal/data: make smaller codec exported api surface
* make key and value sizes serializing bubble up to everything
* Makefile setup & go mod tidy
* Add Unit Test for testing a corrupted config
* Add Unit Test for testing errors from .Stats()
* Refactor Datafile into an interface and add Unit Tests for testing Merge() errors
* Refactor indexer into an interface and add Unit Tests for .Close() errors
* Add Unit Tests for .Delete() errors
* Add Unit Tests for testing Put/Get errors
* Add Unit Test for testing Open errors (bad path for example)
* Refactor out bitcask.writeConfig
* Add more tests for config errors
* Add unit test for options that might error
* Add more test cases for close errors
* Add test case for rotating datafiles
* Fix a possible data race in .Stats()
* Add test case for checksum errors
* Add test case for Sync errors with Put and WithSync enabled
* Refactor and use testify.mock for mocks and generate mocks for all interfaces
* Refactor TestCloseErrors
* Refactored TestDeleteErrors
* Refactored TestGetErrors
* Refactored TestPutErrors
* Refactored TestMergeErrors and fixed a bug with .Fold()
* Add test case for Scan() errors
* Apparently only Scan() can return nil Node()s?
