(For Tea Tuesday this week, I asked my brother, Ian, to fill in while I’m traipsing about the Southeastern United States, and he agreed to write a guest post about his favorite tea-like drink: yerba mate. He’s a freelance journalist, and you can read more of his writing at www.iandoesprojects.com, where he is conducting and documenting “life projects” — finite and arbitrary experiments in doing.) Hi everybody, I’m Ian. You might remember me from that time I went to London and Edinburgh with Emma. I started drinking mate regularly when I studied abroad in Buenos Aires during my junior year of college. I like to say that it’s “a habit…