Fix NoYield to give a useful stack trace in all cases (#27)

Author: LPGhatguy

lib/NoYield.lua

@@ -9,8 +9,8 @@
 
 local function resultHandler(co, ok, ...)
 	if not ok then
-		local err = (...)
-		error(err, 2)
+		local message = (...)
+		error(debug.traceback(co, message), 2)
 	end
 
 	if coroutine.status(co) ~= "dead" then

lib/NoYield.spec.lua

@@ -51,5 +51,6 @@ return function()
 
 		expect(ok).to.equal(false)
 		expect(err:find("foo")).to.be.ok()
+		expect(err:find("NoYield.spec")).to.be.ok()
 	end)
 end