Bump license years for 2017

Per https://www.timeanddate.com/counters/firstnewyear.html, it's already
2017 in a lot of places, so we should bump the Rails license years to
2017.

[ci skip]

MIT-LICENSE

-Copyright (c) 2005-2016 David Heinemeier Hansson
+Copyright (c) 2005-2017 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

actioncable/MIT-LICENSE

-Copyright (c) 2015-2016 Basecamp, LLC
+Copyright (c) 2015-2017 Basecamp, LLC
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

actioncable/lib/action_cable.rb

 #--
-# Copyright (c) 2015-2016 Basecamp, LLC
+# Copyright (c) 2015-2017 Basecamp, LLC
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the

actionmailer/MIT-LICENSE

-Copyright (c) 2004-2016 David Heinemeier Hansson
+Copyright (c) 2004-2017 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

actionmailer/lib/action_mailer.rb

 #--
-# Copyright (c) 2004-2016 David Heinemeier Hansson
+# Copyright (c) 2004-2017 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the

actionpack/MIT-LICENSE

-Copyright (c) 2004-2016 David Heinemeier Hansson
+Copyright (c) 2004-2017 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

actionpack/lib/action_dispatch.rb

 #--
-# Copyright (c) 2004-2016 David Heinemeier Hansson
+# Copyright (c) 2004-2017 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the

actionpack/lib/action_pack.rb

 #--
-# Copyright (c) 2004-2016 David Heinemeier Hansson
+# Copyright (c) 2004-2017 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the

actionview/MIT-LICENSE

-Copyright (c) 2004-2016 David Heinemeier Hansson
+Copyright (c) 2004-2017 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

actionview/lib/action_view.rb

 #--
-# Copyright (c) 2004-2016 David Heinemeier Hansson
+# Copyright (c) 2004-2017 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the

activejob/MIT-LICENSE

-Copyright (c) 2014-2016 David Heinemeier Hansson
+Copyright (c) 2014-2017 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

activejob/lib/active_job.rb

 #--
-# Copyright (c) 2014-2016 David Heinemeier Hansson
+# Copyright (c) 2014-2017 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the

activerecord/MIT-LICENSE

-Copyright (c) 2004-2016 David Heinemeier Hansson
+Copyright (c) 2004-2017 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

activerecord/lib/active_record.rb

 #--
-# Copyright (c) 2004-2016 David Heinemeier Hansson
+# Copyright (c) 2004-2017 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the

activesupport/MIT-LICENSE

-Copyright (c) 2005-2016 David Heinemeier Hansson
+Copyright (c) 2005-2017 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

activesupport/lib/active_support.rb

 #--
-# Copyright (c) 2005-2016 David Heinemeier Hansson
+# Copyright (c) 2005-2017 David Heinemeier Hansson
 #
 # Permission is hereby granted, free of charge, to any person obtaining
 # a copy of this software and associated documentation files (the

railties/MIT-LICENSE

-Copyright (c) 2004-2016 David Heinemeier Hansson
+Copyright (c) 2004-2017 David Heinemeier Hansson
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the