fix splash loading with wx3.0

Previously only gray square was shown. Apparently to show splash screen several calls of wx.Yield() are necessary.
Unfortunately splash.IsShowOnScreen() returns always 1 regardless of whether splash is on the screen or not.
this fix is a dirty hack. It just process all events after splash is created during 0.3 seconds.

from pyjs.jsonrpc import JSONRPCServiceBase

class JSONRPCService(JSONRPCServiceBase):

    def serve(self):
        return self.process(request.body.read())

    def __call__(self,func):
        self.methods[func.__name__]=func
        return func