Automatically convert numeric arguments passed to any Redis commands

[clue]

This changeset makes sure we automatically convert numeric arguments passed to any Redis commands. This is particularly useful when using the new callAsync() method with static analysis tools:

// old (still supported)
$redis->callAsync('SET', 'name', 'Alice', 'EX', '60');

// new
$redis->callAsync('GET', 'name', 'Alice', 'EX', 60);

Builds on top of #166, #140, #128, #127 and others