Understanding two NICs requirement for SQL fail over cluster
First, there's no SQL Server 2013, but the good news is that the version number of SQL Server doesn't matter. It's more based on Windows failover cluster networking, which is explained here in a 3-part series by the Microsoft folks:

http://blogs.technet.com/b/askcore/archive/2010/02/12/windows-server-2008-failover-clusters-networking-part-1.aspx

And then additional info in part 4:

http://blogs.technet.com/b/askcore/archive/2010/04/15/windows-server-2008-failover-clusters-networking-part-4.aspx

Short story - you need some network redundancy, but you don't have to get it with multiple IP addresses. Instead, you get it with network teaming software.