chore: Slightly belatedly update copyright dates.

LICENSE

@@ -1,4 +1,4 @@
-"iperf, Copyright (c) 2014-2018, The Regents of the University of California,
+"iperf, Copyright (c) 2014-2019, The Regents of the University of California,
 through Lawrence Berkeley National Laboratory (subject to receipt of any 
 required approvals from the U.S. Dept. of Energy).  All rights reserved."
 

README.md

@@ -163,7 +163,7 @@ responsibility for the content of these pages.
 Copyright
 ---------
 
-iperf, Copyright (c) 2014-2018, The Regents of the University of
+iperf, Copyright (c) 2014-2019, The Regents of the University of
 California, through Lawrence Berkeley National Laboratory (subject
 to receipt of any required approvals from the U.S. Dept. of
 Energy).  All rights reserved.

docs/conf.py

@@ -45,7 +45,7 @@ master_doc = 'index'
 
 # General information about the project.
 project = u'iperf3'
-copyright = u'2014-2018, ESnet'
+copyright = u'2014-2019, ESnet'
 
 # The version info for the project you're documenting, acts as replacement for
 # |version| and |release|, also used in various other places throughout the