Fixed issue #166.  Decimals and floats will no longer be serialized into XML with scientific notation.

See https://code.google.com/p/pysimplesoap/issues/detail?id=166.
Fixed typo (Decimal instead of decimal)
Merge pull request #25 from SunGard-VPM/null-issues

Issue #166: Prevent scientific notation in decimal & floating point serialization