Dramatic changes

Hi Oshuma,

I changed a lot. Please see the diff.

Of course it's tested.

## Meta changes

* Cleanup code of storages (YAML, Mongo, Memory with Base)
* Added documentation (85% completeness)
* Added some specs for more quality

## New Features

* Module Configurable (see README or code documentation)
* YAML can save changes and creates file if it doesn't exist. (#14)
* Travis-CI support

Note: Class `Memory` is a bit empty after cleanup your code. I think it's no longer needed.