for Debian-based distros, install ca-certificates

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
Merge pull request #33 from alfredodeza/5208

for Debian wheezy, install ca-certificates.
update the docs for a proxy/firewall workaround in wget

Signed-off-by: Alfredo Deza <alfredo@deza.pe>