Removing unnecessary code.

`__set` is a magic method and is not supposed to be called manually
so `$name` is not going to be an array.
Moreover, for anyone who wants to use it manually we have `set` method
which accepts an array as parameter.
Adding support for atomic increment/decrement in sql based databases.
Merge pull request #1122 from farhadi/dev

Adding support for atomic increment/decrement in sql databases