Generalized partially

`partially (f, a, b, c...)` is a function that return the function `f` partially applied with the parameters `a, b, c...`. Example
```
function sumArgs () {
    return R.sum (arguments);
}
var sum6 = partially (sumArgs, 1, 2, 3);
var ten = sum6 (2, 2); //sumArgs (1, 2, 3, 2, 2) = 10;
```
What is more, like `compose` and `pipe`, `partially` is curried with respect to the first parameter, so this serves as a method to create "curried" variadic functions! Example
```
curriedSumArgs= partially (sumArgs);
sum6 = curriedSumArgs (1, 2, 3);
var ten = sum6 (2, 2); //sumArgs (1, 2, 3, 2, 2) = 10;
```
This method is like a `curry2` for variadic functions.