message: update readme now that we dont use proguard on fb4a
diff: @@ -255,16 +255,9 @@ ReDex, however, optimizes .dex bytecode, while ProGuard optimizes .class
  bytecode before it is lowered to .dex. Operating on .dex is sometimes an
  advantage: you can consider the number of virtual registers used by a method
  that is an inlining candidate, and you can control the layout of classes within
  -a dex file. But ProGuard has many capabilities that ReDex does not (for
  +a dex file. But ProGuard has some capabilities that ReDex does not (for
  example, ReDex will not remove unused method parameters, which ProGuard does).
  -In our opinion, comparing ReDex and ProGuard is a bit apples-and-oranges, since
  -we have focused on optimizations that add value on top of ProGuard. We use both
  -tools to optimize the Facebook app. Our reported performance and size
  -improvements (about 25% on both dex size and cold start time) are based on using
  -ReDex on an app already optimized with ProGuard. We have no plans to measure
  -performance without ProGuard.
  -
  ## How about DexGuard?
  DexGuard operates on dex, but we haven't evaluated it at all since it's closed
  