Keep copyright up to date in documentation

Author: Alec Delaney

docs/conf.py

@@ -22,6 +22,7 @@
 #
 import os
 import sys
+import datetime
 
 sys.path.insert(0, os.path.abspath(".."))
 
@@ -77,6 +78,7 @@
 
 # General information about the project.
 project = "Adafruit's DS3231 RTC Library"
+current_year = str(datetime.datetime.now().year)
 copyright = "2016, Philip Moyer"
 author = "Philip Moyer"