Implement Prototype for create()

[searls]

When I call create and pass a prototypal function, I should expect to be returned an object with doubles for each of its prototype's functions.

For instance if I have:

Foo = function(){};
Foo.prototype.bar = function(){};
Foo.prototype.baz = function(){};

Then I should be able to:

testDouble = require('testdouble').create(Foo);
when(testDouble.bar(3)).thenReturn("LOL")
testDouble.bar(3) // "LOL"