Over the past five years, the Southeastern region, led by Atlanta, has gone from being “one of the best kept secrets” in tech, to a vibrant ecosystem teeming with a herd of the billion dollar tech businesses that are referred to in the investment world as “unicorns” (thanks to their supposed rarity). In those five years venture capital investments surged to $2.1 billion in the region, with $1 billion invested in the last year alone, according to Lisa Calhoun, a partner with the Atlanta based investment firm, Valor Ventures. It’s…