Hair care brands are stepping up their digital presence, according to new information from L2, a business intelligence firm that benchmarks the digital performance of brands.   Successful brands, according to the member-based organization, are linking to third-party sellers from brand site, investing heavily in advertising, and also borrowing best practices from their beauty peers.   So which brands are in the top 10? Here’s L2’s ranking, based on each company’s “Digital IQ”:   1. L’...