CHICAGO — The two pieces which make up Hedwig Dances’s spring series are positioned as opposites. The evening, called Sea Level: Above and Below, boasts world premieres by company members Taimy Ramos and Rigoberto Saura. It’s an apt juxtaposition: the murky groundedness of Ramos’s “A Flor de Piel” gives a sense of the dark abyss beneath the ocean’s surface, while Saura’s…