handle: A Range that handles an Exception

When a Exception occurs inside a range chaining the whole chain dies usually. The Handle range fixes that, as it catches a defined exception and calls an user defined handler on it.
Just do `throw new Exception("The last element of the input range to the Handler threw.", caught);`. `Exception` has two constructors:

    @safe pure nothrow this(string msg, string file = __FILE__, size_t line = __LINE__, Throwable next = null)
    @safe pure nothrow this(string msg, Throwable next, string file = __FILE__, size_t line = __LINE__)

Also, I don't think that the message is particularly clear, but I'll have to think a bit about what it should say instead.