Rename _data -> data (public).

The validate module needs to access values for WRONGTYPE test therefore
the underlying data object is now considered public.
Always pass value (strtoint/strtofloat).
Use parseFloat() not Number().

Seems more semantic and correct.
Use util module.
Coerce to string on get.

Allows numeric types to be stored as numbers.
Implement HashMap.valueOf().

Use by the numeric validation logic to get the underlying value of a
command request.
0.1.20
Migrate to module groups.
Use public property for size.

Decrement size in del.
Rename write() to modified().
Support raw db option.

Allows the database class to be used without coercing to string values
on get(). Useful to use as a very simple in-memory store outside of a
server context.
0.1.21
Add rename.
0.1.22
Implement renamenx.