Update librairies + optimizations

loop time and memory optimization

libraries/RTClib/examples/ds1307/ds1307.ino

@@ -0,0 +1,68 @@
+// Date and time functions using a DS1307 RTC connected via I2C and Wire lib
+
+#include <Wire.h>
+#include "RTClib.h"
+
+RTC_DS1307 rtc;
+
+void setup () {
+  Serial.begin(57600);
+#ifdef AVR
+  Wire.begin();
+#else
+  Wire1.begin(); // Shield I2C pins connect to alt I2C bus on Arduino Due
+#endif
+  rtc.begin();
+
+  if (! rtc.isrunning()) {
+    Serial.println("RTC is NOT running!");
+    // following line sets the RTC to the date & time this sketch was compiled
+    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
+    // This line sets the RTC with an explicit date & time, for example to set
+    // January 21, 2014 at 3am you would call:
+    // rtc.adjust(DateTime(2014, 1, 21, 3, 0, 0));
+  }
+}
+
+void loop () {
+    DateTime now = rtc.now();
+    
+    Serial.print(now.year(), DEC);
+    Serial.print('/');
+    Serial.print(now.month(), DEC);
+    Serial.print('/');
+    Serial.print(now.day(), DEC);
+    Serial.print(' ');
+    Serial.print(now.hour(), DEC);
+    Serial.print(':');
+    Serial.print(now.minute(), DEC);
+    Serial.print(':');
+    Serial.print(now.second(), DEC);
+    Serial.println();
+    
+    Serial.print(" since midnight 1/1/1970 = ");
+    Serial.print(now.unixtime());
+    Serial.print("s = ");
+    Serial.print(now.unixtime() / 86400L);
+    Serial.println("d");
+    
+    // calculate a date which is 7 days and 30 seconds into the future
+    DateTime future (now.unixtime() + 7 * 86400L + 30);
+    
+    Serial.print(" now + 7d + 30s: ");
+    Serial.print(future.year(), DEC);
+    Serial.print('/');
+    Serial.print(future.month(), DEC);
+    Serial.print('/');
+    Serial.print(future.day(), DEC);
+    Serial.print(' ');
+    Serial.print(future.hour(), DEC);
+    Serial.print(':');
+    Serial.print(future.minute(), DEC);
+    Serial.print(':');
+    Serial.print(future.second(), DEC);
+    Serial.println();
+    
+    Serial.println();
+    delay(3000);
+}