Dialectic 56: Miles Grimshaw @milesgrimshaw is an investor at @ThriveCapital. He has spent his life hunting change: from "adventure racing" to finding and working with the world's most ambitious companies. His favorite part: getting to go back down the mountain and begin again. I talked to Miles about playing infinite games, seeing greatness up close, and the biggest change he's seen so far: After a career of software investing, all of the underlying assumptions for venture-backed software…