Multi oled support

[basuke]

I tried to use two MicroOLED breakout boards with one Arduino Pro Mini, but it failed. I checked with the library and found begin() was doing wrong. Actually if I split begin() into two parts and call them in that order, it worked.

Not like this to setup():

  oled1.begin();
  oled2.begin();

but like this:

  oled1.setup();
  oled2.setup();

  oled1.initialize();
  oled2.initialize();

Please check the example ino file.