Pull request #21 can cause problems

[pilotak]

I don't think calling _wire->begin(); in ::init() is a good idea in PR #21 . Lets say on ESP8266 you can remap I2C pins and specify different speed so you init the I2C object outside this class and you pass on as reference.

Adafruit_MCP9808 mcp;

void setup() {
    Wire.begin(SDA_2, SCL_2);
    Wire.setClock(400000);

    mcp.begin(&Wire);
}

I think that _wire->begin() should be only in ::begin() and ::begin(uint8_t addr)

[ladyada]

hiya we don't want to break how eveything works, the way you'd do this in ESP is to define a Wire object in the BSP for your pins. maybe you can ask ESP to add a setPins() funciton isntead of overloading begin!