Added _.autoCurry

Added the _.autoCurry which:
Consumes a function (and optional number of arguments - defaults to
function.length)
Produces a functional that will be partially applied until the number of
arguments has been reached.

Example:
var replace = _.autoCurry(function(what, with, string) {return
string.replace(what, with);});

var replaceTest = replace("debug", "");
replaceTest("Testing this debug string");//=> "Testing this string"