Set version to 0.21.0

Author: JoelKatz

src/ripple_data/protocol/BuildInfo.cpp

@@ -25,7 +25,7 @@ char const* BuildInfo::getRawVersionString ()
     //
     //  The build version number (edit this for each release)
     //
-        "0.20.1"
+        "0.21.0"
     //
     //  Must follow the format described here:
     //