Fix for issue #66.

Changed the parameter order to the Sprite constructor when creating a
new sprite for a particle emitter.

Related to
https://github.com/ekelokorpi/panda.js/commit/1847f2f81383f9c1bb408505160eec6dbb549d44
Merge pull request #68 from rcadena/issue-66-particle-error

Fix for issue #66.