Website building platform Squarespace is selling Tock, its restaurant reservation service, to American Express in a deal worth $400 million — the exact figure that Squarespace paid for the service three years ago. Separately, AmEx will be buying Rooam, a mobile payments and ordering platform that integrates with point-of-sale systems. Terms of the Rooam deal were not disclosed. The news comes a month after private equity giant Permira announced plans to acquire Squarespace and take it private in...