Make shouldThrow a template that checks Exception type

[workhorsy]

import BDD;
import std.file : FileException;

unittest {
	describe("BDD#shouldEqual",
		it("Should throw an Exception", delegate() {
			shouldThrow!Exception(delegate() {
				throw new Exception("Smack!");
			}, "Smack!");
		}),
		it("Should fail from wrong exception type", delegate() {
			shouldThrow!FileException(delegate() {
				throw new Exception("Smack!");
			}, "Smack!");
		}),
		it("Should fail from right exception type, but wrong message", delegate() {
			shouldThrow!Exception(delegate() {
				throw new Exception("Boom!");
			}, "Smack!");
		})
	);
}