travis: unshallow repository before calling autogen.sh
travis: unshallow repository before calling autogen.sh

this is a better fix to previous travis failures than setting arbitrary
depth or increasing it for a very large number, because this repo isn't
really large.

rafaelmartins/blogc,blogc/blogc,blogc/blogc,blogc/blogc,rafaelmartins/blogc,rafaelmartins/blogc