Added test target for Rake
Use raw strings for keys and values instead of zero-terminated strings
Avoid closing database more than once
Merge pull request #7 'Fullkeys'

- Adding rake task for tests
- Using raw strings
- Avoid closing db more than once

Thanks @larsch
Load value directly into Ruby string buffer instead of temporary buffer
Merge pull request #8 from larsch/buffer

Load value directly into Ruby string buffer instead of temporary buffer