cer-cert Format not readble

Hi guys,

First thx for that nice exporter it makes my Cert monitoring much easier.

One think, is it possible make it able to read cer and cert format.

Even i see in the code :
extensions = []string{".pem", ".crt", ".cert", ".cer", ".pfx"}

But i get always output error :
glog.Warningf("Couldn't find a CERTIFICATE block in %s", path)

As a workaround i convert cer and cert certificates to pem

Thx guys.