Merge pull request #48 from LowPowerLab/revert-46-master

Revert "Declare RFM69 interrupt with SPI.usingInterrupt()"

RFM69.cpp

@@ -91,9 +91,6 @@ bool RFM69::initialize(uint8_t freqBand, uint8_t nodeID, uint8_t networkID)
   digitalWrite(_slaveSelectPin, HIGH);
   pinMode(_slaveSelectPin, OUTPUT);
   SPI.begin();
-#ifdef SPI_HAS_TRANSACTION
-  SPI.usingInterrupt(_interruptNum);
-#endif
   unsigned long start = millis();
   uint8_t timeout = 50;
   do writeReg(REG_SYNCVALUE1, 0xAA); while (readReg(REG_SYNCVALUE1) != 0xaa && millis()-start < timeout);