Add buffersize support

[6ixfalls]

Assuming that you'd want a parameter passed into every function, optional, stating the buffer size.
Fixes #72.

[kessler]

@6ixfalls thank you for your contribution.

we're having an internal debate here, if passing this parameter to every function is the correct way to implement...
to me it feels like it's an environment thing.

Did you consider it and decided against it or?

[6ixfalls]

After I finished, I kinda thought over and realized that too, though since I had it done already I just made a PR. I could make it a global variable that you set either through a function or variable, which I think would be optimal?

[kessler]

since I made the mistake many years ago not to export an instance of regedit, but rather have all the functions exported directly we are foced to use a "static" variable, in much the same way we implemented setExternalVBSLocation. @M1cr0M1nd will take care of it, I'll leave this PR open until then