Tweak memory alloc and cleanup

[caternuson]

Cleaning up this one too.

#include <Adafruit_BME280.h>

Adafruit_BME280 bme;

void setup() {
  Serial.begin(9600);
  while (!Serial);
  Serial.println(F("BME280 multiple begin() call test"));         
}

void loop() {
  if (!bme.begin()) {
    Serial.println(F("Could not find a valid BME280 sensor, check wiring or "
                      "try a different address!"));
    while (1) delay(10);
  }

  Serial.print(F("Pressure = "));
  Serial.print(bme.readPressure());
  Serial.println(" Pa");

  delay(1000);
}