Featuring one showstopping song after another — “Everything’s Coming Up Roses,” “You Gotta Have a Gimmick,” “Let Me Entertain You” — and based on Gypsy Rose Lee’s memoirs, Gypsy is the story of Lee’s rise to burlesque mega-stardom, with her stage mother — the iconic Mama Rose — behind the curtain. Continuing Lyric Stage’s string of Sondheim musicals, Gypsy showcases the burgeoning lyric-writing abilities of the young composer and lyricist.