Merge lp:~elopio/ubuntu-motd/google-codein into lp:ubuntu-motd

[Leo Arias]

Add the message for google code-in

=== modified file 'index.txt'
--- index.txt	2017-11-14 02:48:20 +0000
+++ index.txt	2017-11-26 01:40:44 +0000
@@ -1,5 +1,5 @@
  * Ubuntu Community Appreciation Day
-   On November 20th we celebrate the diverse community talents that complement
-   Canonical's work on Ubuntu and make it so much more interesting than just an
-   enterprise Linux. Together, we make Ubuntu amazing.
-   - https://ubu.one/ucaday
+   Ubuntu is participating on Google Code-in, a contest to introduce students
+   from 13 to 17 years old to free software. You can join as a student or as a
+   mentor.
+   - https://bit.ly/ucodein