Add spm support

[sorrycc]

A nicer package manager: http://spmjs.io Documentation: http://spmjs.io/documentation

http://spmjs.io/package/klass

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It is a package manager based on Sea.js which is a popular module loader in China.

spmjs focus in browser side. We supply a complete lifecycle managment of package by using spm.

If you need ownership of klass in spmjs, I can add it for your account after signing in http://spmjs.io.