Keep copyright up to date in documentation

Author: Alec Delaney

docs/conf.py

@@ -6,6 +6,7 @@
 
 import os
 import sys
+import datetime
 
 sys.path.insert(0, os.path.abspath(".."))
 
@@ -52,7 +53,8 @@
 
 # General information about the project.
 project = "Adafruit MatrixKeypad Library"
-copyright = "2018 ladyada"
+current_year = str(datetime.datetime.now().year)
+copyright = current_year + " ladyada"
 author = "ladyada"
 
 # The version info for the project you're documenting, acts as replacement for