Store complex object.

With *v* for value, *i* for index (no need to indexOf on delete) and
will add *e* for expiry in ms later.
Do not maintain *i*.

When deleting all subsequent indices would need updating.
Test indexOf() perf.

On this machine a 1MB array of numbers takes about ~14ms to retrieve the
index of the last element when the numbers are coerced to strings, when
numeric the time is about half ~7ms.
Update signature for set.
Assert on key expiry functions.
Assert on expiry command functions.
Assert on setnx command function.
Assert on setex and psetex.
0.1.32
Assert on msetnx.
Comment on msetnx time complexity.
Assert on delExpiredKeys().

Will be used by the server for passive key expiry.
0.1.33
Expose databases getter.
Use setImmediate() in delExpiredKeys().
0.1.34