Issues reading from an I2C device
Looking at the picture, it looks like there is no GND connection between the two boards. You could have a valid GND Connection if the USB cords are on the same bus. Anyways, a dedicated GND connection would do good.
Try to pull up SDA and SCL to Vin
Try using the example from Arduino:



    #include 

void setup()
{
  Wire.begin();        // join i2c bus (address optional for master)
  Serial.begin(9600);  // start Serial for output
}

void loop()
{
  Wire.requestFrom(2, 6);    // request 6 bytes from slave device #2

  while(Wire.available())    // slave may send less than requested
  { 
    char c = Wire.read(); // receive a byte as character
    Serial.print(c);         // print the character
  }

  delay(500);
}




Source: Here