improve proxy example code

[nwolek]

One thing that might have helped when I recently consulted the SDK would be if the example code for adding inlets via proxies actually had multiple proxies here:

https://github.com/Cycling74/max-sdk/blob/master/html/chapter_inout.html#L145

It seems silly that if proxies are most useful for objects with multiple inlets that the example code shows a single proxy.

Consider it a friendly suggestion for your consideration. Take care!

-Nathan