NEW YORK — For those of us of a certain age, it’s hard to imagine Ntozake Shange first wrote the lines “Somebody/ anybody sing a black girl’s song” nearly half a century ago, and made it to Broadway. And beyond. Plenty of 1970s kids in the great Black cities of America — like Chicago and Detroit — remember TV commercials for the first national tour of “For Colored Girls Who Have Considered Suicide / When the Rainbow Is Enuf.” Eyes were pulled from sitcoms and game shows. Back then, the word “choreopoem” meant “closes Saturday” to most Broadway producers, if they knew the term at all. Defining …