Unmarshal Decimal to float instead of string

This pull-request fixes an issue where Decimal values would be returned as strings instead of floats. I guess the PR explains itself :-).

--
        
PHPUnit 3.7.27 by Sebastian Bergmann.

The Xdebug extension is not loaded. No code coverage will be generated.


...............................................................  63 / 158 ( 39%)
............................................................... 126 / 158 ( 79%)
................................

Time: 2.23 seconds, Memory: 12.25Mb

OK (158 tests, 416 assertions)