Array union fix - #243

fixes #242

Updated array check to allow unions and intersections that include an array type.

The one edge case I've seen is an intersection of an array type and an object type that defines numeric keys:

declare function foo(): string[] & {[0]: number, [1]: number};
let a = foo();
let b = a[0];

With this change, the index will get a +1. Whether it should or not is a bit ambiguous to me.