Small change to pushdoc

@valsson what about hardcoding the current variables in case
environment is not defined?

The point is that env var set on travis are not visible, so at some point
we could even forget what are the right settings.

.travis/pushdoc

@@ -54,6 +54,15 @@ This is an auto redirect page.
 </html>
 EOF
 
+if test -z "${GIT_BOT}"
+then
+  export GIT_BOT=plumedbot
+fi
+
+if test -z "${GIT_BOT_EMAIL}"
+then
+  export GIT_BOT_EMAIL=giovanni.bussi+plumedbot@gmail.com
+fi
 
 git init
 git config user.email "${GIT_BOT_EMAIL}"