Fix for new Function calls

[liborm85]

Fixes#28

[blikblum]

Hi i take a look at the code and it can be simplified a bit:

constructor(type,versions={}){super();this.type=type;this.versions=versions;}decode(stream,parent,length=0){constres=this._setup(stream,parent,length);if(typeofthis.type==='string'){res.version=parent[this.type];}else{res.version=this.type.decode(stream);}

Instead of calling versionGetter method, do the operation inline. versionSetter is not used at all.

Did not test because internet connection is far from great where i am.

Feel free to use it

[liborm85]

New PR #37
Tests passed. Thanks.