bmp180: change method names/signature for obtaining temperature and pressure uniform with other similar drivers

Signed-off-by: Ron Evans <ron@hybridgroup.com>

README.md

@@ -39,10 +39,10 @@ func main() {
     println("BMP180 detected")
 
     for {
-        temp, _ := sensor.Temperature()
+        temp, _ := sensor.ReadTemperature()
         println("Temperature:", float32(temp)/1000, "ºC")
 
-        pressure, _ := sensor.Pressure()
+        pressure, _ := sensor.ReadPressure()
         println("Pressure", float32(pressure)/100000, "hPa")
 
         time.Sleep(2 * time.Second)